Great day out with close-ups of the ducks, geese, moorhens, etc.
Showing posts with label Geese. Show all posts
Showing posts with label Geese. Show all posts
Saturday, 27 June 2015
Sunday, 3 May 2015
Whitethroats and Sand Martins at Leybourne Lakes
Quite a few Whitethroats, Sylvia communis, were to be found, defending territories or setting up nests.
I think the one I was photographing here from the first bridge across the stream might perhaps be a male, as although its head wasn't so clearly grey as I would have expected, it wasn't truly brown either. There is quite a clear eye-ring, and I rather think that the brown on the head might be superficial and might be about to wear off. It is still quite early in the season, and most of the females have perhaps not arrived yet. It is known that the males arrive first, and prepare "cock-nests" for the approval of the female. This bird does seem to be the same bird throughout (there appears to be a dimple in the forehead just to the left of the beak in at least some photos), there was a distinct pinkish tinge to the breast, and it was singing well in between visits to the nest, on the other side of the stream, so it is at least possible that it is a male.
The next two pictures are perhaps more clearly a male, if indeed it is the same bird!! To be honest the only thing I can really suggest is that it is an adult, partly because it must be as it is nest building, but also because the iris is not anywhere as dark a brown as would be expected in a juvenile bird, and so the light brown of the iris clearly contrasts with the dark pupil in the centre! The inside of the eyelid is said to be reddish, and I wouldn't strongly disagree, although I wouldn't strongly confirm either!
The beak is also quite well shown in the picture below. The upper mandible is dark horn, the lower is flesh-yellow except at the tip where it is also dark horn. The cutting edges are flesh-yellow. The inside of the mouth is yellow-pink.
The legs are brown (not as pale brown as I have read) with the toes perhaps slightly darker.
In the nominate subspecies, Sylvia communis communis, the moulting process is a complete moult post-breeding before migration, although perhaps partly suspended for the migration period, and then a partial moult pre-breeding. In the Eastern subspecies, volgensis, rubicola and icterops, the post-breeding moult is partial, and the pre-breeding moult complete.
Nominate males then arrive on the breeding ground with fresh head and body plumage, i.e, the head and body will tend to be browner than the text-books generally suggest. The wings and tail are likely to be more worn, perhaps explaining why it is very difficult to see the normally stated white edging to the tail in this particular bird.
The post-breeding moult is primaries and secondaries descendent, working from P1 outwards towards P10, and S1 outwards towards S6. The suspension of moulting, if it occurs, is more likely to delay the moulting of the secondaries than the primaries.
While I was watching the whitethroat, there was also a Moorhen fussing about on the bank, before it slowly swam off.
The Muscovy Duck was by the feeding area:
The Greylag Geese were present in small numbers around the feeding area, looking in good condition.
One pair had three fairly new goslings.
The Mallards are looking well paired up, and svelte! Here is a drake.
There was one Muscovy drake as well.
Way out in the middle of the Ocean, there were Sand Martins skimming over the water and feeding, but too far away to be more than a blur in the photo.
There was an Andrena species female solitary bee in the shelter by the side of The Ocean, with a shiny black top to the abdomen, but I couldn't be sure of the species. Quite possibly Andrena nitida? (2021 guess).
I think the one I was photographing here from the first bridge across the stream might perhaps be a male, as although its head wasn't so clearly grey as I would have expected, it wasn't truly brown either. There is quite a clear eye-ring, and I rather think that the brown on the head might be superficial and might be about to wear off. It is still quite early in the season, and most of the females have perhaps not arrived yet. It is known that the males arrive first, and prepare "cock-nests" for the approval of the female. This bird does seem to be the same bird throughout (there appears to be a dimple in the forehead just to the left of the beak in at least some photos), there was a distinct pinkish tinge to the breast, and it was singing well in between visits to the nest, on the other side of the stream, so it is at least possible that it is a male.
The next two pictures are perhaps more clearly a male, if indeed it is the same bird!! To be honest the only thing I can really suggest is that it is an adult, partly because it must be as it is nest building, but also because the iris is not anywhere as dark a brown as would be expected in a juvenile bird, and so the light brown of the iris clearly contrasts with the dark pupil in the centre! The inside of the eyelid is said to be reddish, and I wouldn't strongly disagree, although I wouldn't strongly confirm either!
The beak is also quite well shown in the picture below. The upper mandible is dark horn, the lower is flesh-yellow except at the tip where it is also dark horn. The cutting edges are flesh-yellow. The inside of the mouth is yellow-pink.
The legs are brown (not as pale brown as I have read) with the toes perhaps slightly darker.
In the nominate subspecies, Sylvia communis communis, the moulting process is a complete moult post-breeding before migration, although perhaps partly suspended for the migration period, and then a partial moult pre-breeding. In the Eastern subspecies, volgensis, rubicola and icterops, the post-breeding moult is partial, and the pre-breeding moult complete.
Nominate males then arrive on the breeding ground with fresh head and body plumage, i.e, the head and body will tend to be browner than the text-books generally suggest. The wings and tail are likely to be more worn, perhaps explaining why it is very difficult to see the normally stated white edging to the tail in this particular bird.
The post-breeding moult is primaries and secondaries descendent, working from P1 outwards towards P10, and S1 outwards towards S6. The suspension of moulting, if it occurs, is more likely to delay the moulting of the secondaries than the primaries.
While I was watching the whitethroat, there was also a Moorhen fussing about on the bank, before it slowly swam off.
The Muscovy Duck was by the feeding area:
The Greylag Geese were present in small numbers around the feeding area, looking in good condition.
One pair had three fairly new goslings.
The Mallards are looking well paired up, and svelte! Here is a drake.
There was one Muscovy drake as well.
Way out in the middle of the Ocean, there were Sand Martins skimming over the water and feeding, but too far away to be more than a blur in the photo.
There was an Andrena species female solitary bee in the shelter by the side of The Ocean, with a shiny black top to the abdomen, but I couldn't be sure of the species. Quite possibly Andrena nitida? (2021 guess).
Tuesday, 16 December 2014
Reculver on another lovely day, with Brent Geese
Black-headed and Herring Gulls, and one Oystercatcher with the Geese, with Cormorants out to sea. A Pied Wagtail and a Blackbird by St Mary's. I thought there was a Pipit along the wall by the Oyster Farm. At least a score of Linnets by Coldharbour, feeding on the bank by the bunded pools, together with half a dozen Redshank, both seen and heard, and two Black-headed Gulls.
I was moving fairly quickly, but thought I might also have seen a Stonechat behind Coldharbour, just from an impression of a shape, coupled with a perch high on a bush - weak evidence I know!
About 540 Dark-bellied Brent Geese on the fields and commuting to and from a gravel bank on the beach, lovely to see, and hear! Their almost grunting (the BBC suggests "gobbling") calls are surprisingly attractive and restful. BWP has them characteristically noisier on water, and indeed it was while they were on the sea, or flying from the sea that I heard them calling (BWP = hronk, hronk)! I also thought I saw one Pale-bellied Brent Goose, as regularly reported here, but it was difficult to be really sure. The birds were quite mobile, first disturbed from the field, and then moving in smaller groups backwards and forwards from the shingle bank by the Coldharbour outfall into the fields, including the one by the Green Bank. It was noteworthy that they flew quite low and in loose "brunches" or long "lines" rather than V-shaped skeins.
They lead lives that are so close to the edge. Average annual winter mortality in the UK is estimated to be about 15%, although a typical life span may be as long as 11 years, and the current BTO record being over 28 years old. On their long migration it is essential that they arrive on the breeding grounds in as good a condition as possible. On the breeding grounds they may first eat mosses and lichens, then turning to grass as it becomes more available. They need to have nutritional reserves to see them through problems such as any remaining snow and ice. It seems that individual birds that have better access to food within the flock, and therefore build up heavier body masses on the spring staging areas show better reproductive success. The females seem to get about half their energy for incubation from stored endogenous sources, the other half from intensive feeding episodes the length of which depend on the threat from weather, etc (Inger et al, 2008). It is suggested that an increase of body mass of one sixth on migration may lead to raising breeding success from 8% to 65%. However I think birds should not be too heavy before long distance flights, or they will have potential problems migrating.
Marine habitats seem to be greatly preferred by Brent Geese over terrestrial food sources for quality. Best food sources are Zostera spp., Eelgrass, Ulva sp, Sea Lettuce and Enteromorpha spp, The rationale is that these algae are easier to digest than the fibre-rich grass, particularly important in geese, which have rather inefficient digestive systems.
Increasingly as the migratory populations have grown over the years from the nadir of the '30s, (10 fold perhaps?), Brents are apparently being forced onto (or are turning to) farmland rather than the Zostera or Enteromorpha rich intertidal zone. This may in the longer run have impacts on the average reproductive success of the populations. I wasn't paying proper attention today or I would have been surer of their detailed behaviour. The little I did see suggested that the Brents at Reculver were perhaps feeding a bit while they were on the autumn sown cereal (wheat?) and definitely often interacting aggressively. While they were on the seashore, they didn't seem to be feeding, or indeed showing too much aggression to each other, but I should have been actively checking. The flock was fairly densely packed on the sea and I wouldn't have thought there was anything for them to eat where they were anyway, perhaps a little Enteromorpha. They seemed more to be having a bit of a "little seaside break".
Normal food sources start off with Zostera, Eel Grass. In early winter the Zostera spp. beds are relatively intact and the rhizome, in particular, provides an important food resource (Mathers et al. 1998). In late winter, however, the availability of Zostera spp. declines, as a result of foraging and senescence, and it is more patchily distributed. Presumably there is Zostera, Ulva or Enteromorpha somewhere around off Reculver or Minnis Bay?? Perhaps they spend most of their feeding time on the fields?
At this time of year the flocks may consist of mixed ages, including the yearlings, if any are present - again I didn't really look at the time! The first winter birds are similar to the adults, although the white neck markings are less conspicuous, the white tipped coverts of the juveniles are largely retained and there is rather less white edging to the flanks. In retrospect I think I did see the white-tipped coverts indicating first winter birds in a number of cases.
The social inequities will mean that the higher-ranked individuals get the better resources in a feeding flock. It seems that in the winter period at least, families with any number of juveniles dominate pairs, pairs dominate singletons, and males dominate females. Several of these characters correlate with breeding success, and may be difficult to disentangle. Another paper suggested that large families do control more feeding resources than small ones, leading to less cost to the increased parental investment, so that things balance out. However by springtime arrival on the breeding grounds, the yearlings will apparently have been excluded from the family and the more mature birds will have settled into their pairbonds again. The pairings give advantages to the females of the pair, as the males protect them from aggressive behaviour from the other birds, allowing the females longer to feed up. BWP also notes that the birds are monogamous and pair for life!
The behaviour of the birds on the Arctic breeding grounds is extremely interesting. Laying is quite synchronous over a wide area - but do young birds lay later than experienced ones? The sites chosen will generally be on the drier hummocks to avoid melt flooding, perhaps on islands. The nests shaped like shallow bowls are about 30 cm. across, the internal bowl about 6 cm deep, of about 20 cm. diameter. They may be roughly 25 m. apart. Both sexes build the nest, using nearby materials, lining the nest with moss and grass, and covering with a fair amount of down. Incubation starts when the last egg is laid, leading to synchronous hatching. The nests may be re-used from year to year. Breeding success ranges are the most variable of all Arctic Geese, as calculated by the numbers of yearlings in winter flocks in the UK ranging from 1% to 45%. Up to 4 eggs are laid, generally only in one batch.
Like most, but not all, Arctic geese, the females have to eat as well as incubate. They cover the eggs with down and then move off the nest to feed, pecking virtually continuously and quite close to the nest, thus maximising food intake. The males do not incubate, but take on a protective role, against predators and conspecifics, being relatively more alert while the female is feeding, and feeding relatively more while the female is incubating. Once the chicks are hatched, both parents remain protective, although they do not need to feed the young as the chicks are precocial, nidifugous and self-feeding.
They tend to have two brood attempts, and then moult all in a narrow time window, before migrating, quite a challenge!?
The recorded numbers of these geese at Reculver do seem to fluctuate considerably. Chris Hindle's blog suggests that numbers in November 2014 were up to a thousand or so, but they seem to be down to 400 - 500 now in December 2014. They may disperse quite widely, moving onto other areas according to the weather, or food resources. They may perhaps move to Chichester or Harbour on the South Coast, or the French coast at Morbihan for example.
Boorman and Ranwell (1977) summarised much of information held about Brent Geese at that time, in their ITE paper scoping the possible environmental impact of the construction of Maplin Airport on the East Coast, never implemented in the end thank goodness. They showed that at least 20% of the world's population of Brent Geese (40% of the UK population) used the area over at least part of the winter, normally the first part.
In the 1930s the Eelgrass Zostera species had been hit by a disease that greatly lowered their populations, particularly Z. marina. Anecdotal accounts suggested that the Brent Geese had been hit as well, but the reduction cannot now be quantified. Between the 1950s and 1970s populations increased to about 25,000 - 30,000, contemporaneously with the introduction of shooting bans in the 1950s in the main European countries used as migration routes. It was thought that the population increases were being, or would be, limited by land reclamations in various European countries, particularly the Netherlands. However between 1968 and 1973 the world population more than doubled, shooting up to about 68,000 birds, while at the same time they started using farmland sources of winter food!
In the Maplin study, in the first half of winter, September to January, over half the Essex population fed on the Zostera beds of Foulness and Leigh, then moving on to the Enteromorpha beds of the other estuaries. In January/February '72-3, with peak counts double the previous year, about 30% of the birds turned to farmland, a behaviour only previously noted in the freezing winter of '62-3. In 1973-74, at very high populations, weight losses in birds averaging about 9% were noted. These losses could significantly impact upon reproductive success. By contrast in '62-63 in Denmark, with about a third of the 73-74 populations, despite the terrible weather, no weight losses were found.
ITE then organised some ground-breaking netting and ringing to try to understand the movements of the geese. Cannon netting had to be used on the open flats, based on siting the cannon nets in advance, hoping to guess where the geese might be. Only about 16 individual Brent Geese had ever been ringed before, so little was known of their winter distribution changes. In this exercise one family was noted to move North to the Blackwater, then South to Chichester Harbour, and then finally on to the Waddensee within 24 hours of leaving Chichester - interesting to see how they stuck together. Of course such familial cohesion is essential. Juveniles feed for up to 95% of their time presumably being partly watched over by their parents, who feed for about 75% of their time early in the winter, although this trends to 95% later in the year, as food quantity and quality decreases. The ringing demonstrated that at least some birds remained relatively faithful to their sites on particular estuaries at least for some time.
Brent geese have very variable breeding results according to the weather and predation. In the year 1977 it was estimated that successful breeding had occurred in only 8 of the previous 15 years. No other goose species has such a variable breeding success leading to unbalanced age class structures
in the population from year to year, likely to affect social behaviour. In years with success, the family groups migrate together, adults with that year's juveniles. In unsuccessful years the (non)breeding adults migrated before the two year old birds.
The approximate age composition of the British population of Dark-bellied Brent geese was calculated for 1973-74 by the ITE. The total population was estimated then at roughly 41,000, with about 15,400 first-winter birds, 7,600 breeding adults and 18,000 full grown birds without young (from the estimated mean brood size of 4.0 and the estimated percentage of first winter birds as 37.5). The full grown birds without young were probably mostly in their second winter, for Brent geese do not usually breed until their third or fourth summer.
It is worth noting that the latest BTO population estimate is in the region of 95,000 Dark-bellied birds wintering in the UK! There are also about 27,000 Canadian Light-bellied Brent Geese and 3,400 Svalbard Light-bellied Brent Geese. The main concentrations of Dark-bellied birds are in the Wash, the North Norfolk coastal marshes, Essex estuaries, the Thames Estuary and Chichester and Langstone Harbours.
The ITE trials demonstrated that disturbance by humans or light aircraft caused the geese to stop feeding or fly, reducing their feeding success by 3 - 4 percent, which might seem low, although any reduction may be very significant. Using a nightscope it was established that the Brent Geese did feed at night throughout the winter, sometimes in cloudy weather, as well as during the day, and in some cases on quite sparse Enteromorpha. However, Brent geese appeared not to feed so intensely at night as during the day, and were almost exclusively confined to the tide edge.
Clearly the farm cereals and grasses are not going to be anywhere near as nutritional as Zostera, and the balance between energy expanded, and energy gained while feeding may be greatly narrowed. It is also worth remembering that extended periods of frost may mean that the farmland resources become completely unavailable for a period! I wonder how the Reculver Geese did over the severe winters of 2011/2012 and 2012/13. The impact of switching to farm resources on individual fitness is certainly of some potential concern.
The amount of Zostera, or Enteromorpha, likely to be available in future years is not necessarily predictable. Particular species appear to have very finely attuned requirements for drainage/drying out of the substrate, and the balance between accretion and erosion. These factors may be affected by other changes along the coast, and climate. Zostera noltii of the intertidal zone appears to be the currently preferred species for Brent Geese, with the role of the subtidal Z. marina var. angustifolia now less well understood. Coastal squeeze and shore steepening may impact on Zostera beds as well as salt marsh availability.
These are monthly peak counts for Brents at Reculver. 2008/09 was a relatively poor year across North Kent, but not too bad at Reculver. Interestingly the winter of 2011/12 gave high numbers, but the significantly colder winter of 2012/13 (at least in the East and Southeast) gave only the "normal" moderate numbers.
Bibliography:
Boorman, L.A. and Ranwell, D.S. (1977) The ecology of Maplin Sands and the coastal zones of
Suffolk, Essex and North Kent. Institute of Terrestrial Ecology, Cambridge.
Birds of the Western Palaearctic (BWP).
I was moving fairly quickly, but thought I might also have seen a Stonechat behind Coldharbour, just from an impression of a shape, coupled with a perch high on a bush - weak evidence I know!
About 540 Dark-bellied Brent Geese on the fields and commuting to and from a gravel bank on the beach, lovely to see, and hear! Their almost grunting (the BBC suggests "gobbling") calls are surprisingly attractive and restful. BWP has them characteristically noisier on water, and indeed it was while they were on the sea, or flying from the sea that I heard them calling (BWP = hronk, hronk)! I also thought I saw one Pale-bellied Brent Goose, as regularly reported here, but it was difficult to be really sure. The birds were quite mobile, first disturbed from the field, and then moving in smaller groups backwards and forwards from the shingle bank by the Coldharbour outfall into the fields, including the one by the Green Bank. It was noteworthy that they flew quite low and in loose "brunches" or long "lines" rather than V-shaped skeins.
They lead lives that are so close to the edge. Average annual winter mortality in the UK is estimated to be about 15%, although a typical life span may be as long as 11 years, and the current BTO record being over 28 years old. On their long migration it is essential that they arrive on the breeding grounds in as good a condition as possible. On the breeding grounds they may first eat mosses and lichens, then turning to grass as it becomes more available. They need to have nutritional reserves to see them through problems such as any remaining snow and ice. It seems that individual birds that have better access to food within the flock, and therefore build up heavier body masses on the spring staging areas show better reproductive success. The females seem to get about half their energy for incubation from stored endogenous sources, the other half from intensive feeding episodes the length of which depend on the threat from weather, etc (Inger et al, 2008). It is suggested that an increase of body mass of one sixth on migration may lead to raising breeding success from 8% to 65%. However I think birds should not be too heavy before long distance flights, or they will have potential problems migrating.
Marine habitats seem to be greatly preferred by Brent Geese over terrestrial food sources for quality. Best food sources are Zostera spp., Eelgrass, Ulva sp, Sea Lettuce and Enteromorpha spp, The rationale is that these algae are easier to digest than the fibre-rich grass, particularly important in geese, which have rather inefficient digestive systems.
Increasingly as the migratory populations have grown over the years from the nadir of the '30s, (10 fold perhaps?), Brents are apparently being forced onto (or are turning to) farmland rather than the Zostera or Enteromorpha rich intertidal zone. This may in the longer run have impacts on the average reproductive success of the populations. I wasn't paying proper attention today or I would have been surer of their detailed behaviour. The little I did see suggested that the Brents at Reculver were perhaps feeding a bit while they were on the autumn sown cereal (wheat?) and definitely often interacting aggressively. While they were on the seashore, they didn't seem to be feeding, or indeed showing too much aggression to each other, but I should have been actively checking. The flock was fairly densely packed on the sea and I wouldn't have thought there was anything for them to eat where they were anyway, perhaps a little Enteromorpha. They seemed more to be having a bit of a "little seaside break".
Normal food sources start off with Zostera, Eel Grass. In early winter the Zostera spp. beds are relatively intact and the rhizome, in particular, provides an important food resource (Mathers et al. 1998). In late winter, however, the availability of Zostera spp. declines, as a result of foraging and senescence, and it is more patchily distributed. Presumably there is Zostera, Ulva or Enteromorpha somewhere around off Reculver or Minnis Bay?? Perhaps they spend most of their feeding time on the fields?
At this time of year the flocks may consist of mixed ages, including the yearlings, if any are present - again I didn't really look at the time! The first winter birds are similar to the adults, although the white neck markings are less conspicuous, the white tipped coverts of the juveniles are largely retained and there is rather less white edging to the flanks. In retrospect I think I did see the white-tipped coverts indicating first winter birds in a number of cases.
The social inequities will mean that the higher-ranked individuals get the better resources in a feeding flock. It seems that in the winter period at least, families with any number of juveniles dominate pairs, pairs dominate singletons, and males dominate females. Several of these characters correlate with breeding success, and may be difficult to disentangle. Another paper suggested that large families do control more feeding resources than small ones, leading to less cost to the increased parental investment, so that things balance out. However by springtime arrival on the breeding grounds, the yearlings will apparently have been excluded from the family and the more mature birds will have settled into their pairbonds again. The pairings give advantages to the females of the pair, as the males protect them from aggressive behaviour from the other birds, allowing the females longer to feed up. BWP also notes that the birds are monogamous and pair for life!
The behaviour of the birds on the Arctic breeding grounds is extremely interesting. Laying is quite synchronous over a wide area - but do young birds lay later than experienced ones? The sites chosen will generally be on the drier hummocks to avoid melt flooding, perhaps on islands. The nests shaped like shallow bowls are about 30 cm. across, the internal bowl about 6 cm deep, of about 20 cm. diameter. They may be roughly 25 m. apart. Both sexes build the nest, using nearby materials, lining the nest with moss and grass, and covering with a fair amount of down. Incubation starts when the last egg is laid, leading to synchronous hatching. The nests may be re-used from year to year. Breeding success ranges are the most variable of all Arctic Geese, as calculated by the numbers of yearlings in winter flocks in the UK ranging from 1% to 45%. Up to 4 eggs are laid, generally only in one batch.
Like most, but not all, Arctic geese, the females have to eat as well as incubate. They cover the eggs with down and then move off the nest to feed, pecking virtually continuously and quite close to the nest, thus maximising food intake. The males do not incubate, but take on a protective role, against predators and conspecifics, being relatively more alert while the female is feeding, and feeding relatively more while the female is incubating. Once the chicks are hatched, both parents remain protective, although they do not need to feed the young as the chicks are precocial, nidifugous and self-feeding.
They tend to have two brood attempts, and then moult all in a narrow time window, before migrating, quite a challenge!?
The recorded numbers of these geese at Reculver do seem to fluctuate considerably. Chris Hindle's blog suggests that numbers in November 2014 were up to a thousand or so, but they seem to be down to 400 - 500 now in December 2014. They may disperse quite widely, moving onto other areas according to the weather, or food resources. They may perhaps move to Chichester or Harbour on the South Coast, or the French coast at Morbihan for example.
Boorman and Ranwell (1977) summarised much of information held about Brent Geese at that time, in their ITE paper scoping the possible environmental impact of the construction of Maplin Airport on the East Coast, never implemented in the end thank goodness. They showed that at least 20% of the world's population of Brent Geese (40% of the UK population) used the area over at least part of the winter, normally the first part.
In the 1930s the Eelgrass Zostera species had been hit by a disease that greatly lowered their populations, particularly Z. marina. Anecdotal accounts suggested that the Brent Geese had been hit as well, but the reduction cannot now be quantified. Between the 1950s and 1970s populations increased to about 25,000 - 30,000, contemporaneously with the introduction of shooting bans in the 1950s in the main European countries used as migration routes. It was thought that the population increases were being, or would be, limited by land reclamations in various European countries, particularly the Netherlands. However between 1968 and 1973 the world population more than doubled, shooting up to about 68,000 birds, while at the same time they started using farmland sources of winter food!
In the Maplin study, in the first half of winter, September to January, over half the Essex population fed on the Zostera beds of Foulness and Leigh, then moving on to the Enteromorpha beds of the other estuaries. In January/February '72-3, with peak counts double the previous year, about 30% of the birds turned to farmland, a behaviour only previously noted in the freezing winter of '62-3. In 1973-74, at very high populations, weight losses in birds averaging about 9% were noted. These losses could significantly impact upon reproductive success. By contrast in '62-63 in Denmark, with about a third of the 73-74 populations, despite the terrible weather, no weight losses were found.
ITE then organised some ground-breaking netting and ringing to try to understand the movements of the geese. Cannon netting had to be used on the open flats, based on siting the cannon nets in advance, hoping to guess where the geese might be. Only about 16 individual Brent Geese had ever been ringed before, so little was known of their winter distribution changes. In this exercise one family was noted to move North to the Blackwater, then South to Chichester Harbour, and then finally on to the Waddensee within 24 hours of leaving Chichester - interesting to see how they stuck together. Of course such familial cohesion is essential. Juveniles feed for up to 95% of their time presumably being partly watched over by their parents, who feed for about 75% of their time early in the winter, although this trends to 95% later in the year, as food quantity and quality decreases. The ringing demonstrated that at least some birds remained relatively faithful to their sites on particular estuaries at least for some time.
Brent geese have very variable breeding results according to the weather and predation. In the year 1977 it was estimated that successful breeding had occurred in only 8 of the previous 15 years. No other goose species has such a variable breeding success leading to unbalanced age class structures
in the population from year to year, likely to affect social behaviour. In years with success, the family groups migrate together, adults with that year's juveniles. In unsuccessful years the (non)breeding adults migrated before the two year old birds.
The approximate age composition of the British population of Dark-bellied Brent geese was calculated for 1973-74 by the ITE. The total population was estimated then at roughly 41,000, with about 15,400 first-winter birds, 7,600 breeding adults and 18,000 full grown birds without young (from the estimated mean brood size of 4.0 and the estimated percentage of first winter birds as 37.5). The full grown birds without young were probably mostly in their second winter, for Brent geese do not usually breed until their third or fourth summer.
It is worth noting that the latest BTO population estimate is in the region of 95,000 Dark-bellied birds wintering in the UK! There are also about 27,000 Canadian Light-bellied Brent Geese and 3,400 Svalbard Light-bellied Brent Geese. The main concentrations of Dark-bellied birds are in the Wash, the North Norfolk coastal marshes, Essex estuaries, the Thames Estuary and Chichester and Langstone Harbours.
The ITE trials demonstrated that disturbance by humans or light aircraft caused the geese to stop feeding or fly, reducing their feeding success by 3 - 4 percent, which might seem low, although any reduction may be very significant. Using a nightscope it was established that the Brent Geese did feed at night throughout the winter, sometimes in cloudy weather, as well as during the day, and in some cases on quite sparse Enteromorpha. However, Brent geese appeared not to feed so intensely at night as during the day, and were almost exclusively confined to the tide edge.
Clearly the farm cereals and grasses are not going to be anywhere near as nutritional as Zostera, and the balance between energy expanded, and energy gained while feeding may be greatly narrowed. It is also worth remembering that extended periods of frost may mean that the farmland resources become completely unavailable for a period! I wonder how the Reculver Geese did over the severe winters of 2011/2012 and 2012/13. The impact of switching to farm resources on individual fitness is certainly of some potential concern.
The amount of Zostera, or Enteromorpha, likely to be available in future years is not necessarily predictable. Particular species appear to have very finely attuned requirements for drainage/drying out of the substrate, and the balance between accretion and erosion. These factors may be affected by other changes along the coast, and climate. Zostera noltii of the intertidal zone appears to be the currently preferred species for Brent Geese, with the role of the subtidal Z. marina var. angustifolia now less well understood. Coastal squeeze and shore steepening may impact on Zostera beds as well as salt marsh availability.
These are monthly peak counts for Brents at Reculver. 2008/09 was a relatively poor year across North Kent, but not too bad at Reculver. Interestingly the winter of 2011/12 gave high numbers, but the significantly colder winter of 2012/13 (at least in the East and Southeast) gave only the "normal" moderate numbers.
Bibliography:
Boorman, L.A. and Ranwell, D.S. (1977) The ecology of Maplin Sands and the coastal zones of
Suffolk, Essex and North Kent. Institute of Terrestrial Ecology, Cambridge.
Birds of the Western Palaearctic (BWP).
Monday, 27 January 2014
Barden Lake at Haysden slowly drying out again as the floods recede slightly.
The water level in Barden Lake has slowly and gently dropped, and you can now walk all the way around, muddy though it is. On the Fishing Lake by the cafe block, there were some a couple of nice Tufted Ducks, Aythya fuligula, 2 males. This bird does not have an obvious crest, but I think must still be older than a first winter juvenile, as there is no barring on the flanks. The water droplets still clinging to the feathers may indicate that the bird has recently surfaced and the crest may then be slicked down in consequence.
Other interesting ID features are the interestingly shaped head with the high forehead on a relatively narrow neck. The bill has a good solid black tip or nail (across the cross-section of the bill, looking as though it "has been dipped in ink"). There is more than a hint of a whitish stripe across the front of the bill, contrasting with the blue-grey on the rear part of the bill. The bird is said to sit low in the water but with its tail above the surface, and I think I would agree with this from this picture to some extent - it looks as though its sitting a bit lower in the water at the moment, per haps after a dive. Deep yellow eye, perhaps slightly out of focus. The contrast between the dark wing and the white sides is nice and distinct, a beautiful bird indeed, moving well across the water!.
On the main Gravel Pit, Barden Lake, other individuals were keeping themselves out of trouble. This one looks very much at rest, but with its eyes open! I think that the wings are most easily seen from this angle, with the two sets of primary feathers forming a valley down the back between the two wings. It also looks to me as though the flank feathers somewhat overlie the sides of the wings, giving that fringed effect to the rear of the white sides. The tail sits slightly cocked in this picture.
According to the BTO, "the rapid expansion of the Tufted Duck in Britain during the late 19th/early 20th century is probably due to the colonisation of Britain by Zebra Mussels (brought into London docks in the 1820s)". The birds are omnivorous, feeding mainly on mussels, insects and plant material taken from the muddy bottoms of the water bodies they are on, diving anywhere between 4 - 15 metres down. It breeds better if there aren't excessive numbers of fish.
The females show the same amount of darkening at the top of the biill, with a little light band just behind. Some of them show a scaup-like white patch at the base of the bill, although not quite so extensive, and I rather think quite a lot of them show some degree of lighter brown in that area, like the one in the duck below.
Sunday, 19 January 2014
Wet but bright at Haysden
The paths were still under water, but the sun was shining, and it was actually quite warm. The Gulls and geese were showing well, but it was very busy and there were few ducks to be seen.
This gull is stabilising itself with its wings, in order to duck its head below the surf\ace in a very rapid movement. A skirt of water flies up past its head!
This one is demonstrating its STOL capabilities
and this one looks as though its just blown a huge bubble!
Further around the lake, there were some Tufted Duck, Aythya fuligola, quite a way out on the water from the bird feeding stage. The males were showing off their crests dramatically, as in the picture taken below. This bird looks as though it is riding high in the water, with the tail clearly visible. It doesn't look as though it has dived for quite a while!
Saturday, 28 December 2013
Leybourne again
Trying out the monopod today I did think it made a difference, until I forgot to point the autofocus spot directly onto the birds concerned. However, here is a fairly sharp Greylag, Anser anser, from quite close-up,
There were also about 60 Canada Geese, Branta canadensis, Mute Swans, Cygnus olor, many Black-headed Gulls, Chroicocephalus ridibundus, some Herring Gulls, Larus argentatus, and at least one Common Gull, Larus canus. Also Mallard, Anas platyrynchos, Tufted Duck, Aythya fuligola, one Drake Shoveller, Anas clypeata, several Great Crested Grebe, Podiceps cristata, Cormorants, Phalocrocorax carbo, Moorhens, Gallinula chloropus, and Coots, Fulica atra.
This is a one year old Black-headed Gull, as indicated by the brown on the wings, and the slightly orange bill
Whereas this is an adult bird with a much darker red bill and perhaps a tendency to achieve breeding plumage a bit earlier.
There were also about 60 Canada Geese, Branta canadensis, Mute Swans, Cygnus olor, many Black-headed Gulls, Chroicocephalus ridibundus, some Herring Gulls, Larus argentatus, and at least one Common Gull, Larus canus. Also Mallard, Anas platyrynchos, Tufted Duck, Aythya fuligola, one Drake Shoveller, Anas clypeata, several Great Crested Grebe, Podiceps cristata, Cormorants, Phalocrocorax carbo, Moorhens, Gallinula chloropus, and Coots, Fulica atra.
This is a one year old Black-headed Gull, as indicated by the brown on the wings, and the slightly orange bill
Whereas this is an adult bird with a much darker red bill and perhaps a tendency to achieve breeding plumage a bit earlier.
This is an adult Herring Gull, only just in focus,
Herring Gull calling, much more heavily cropped:
Moorhen:
Tufted Duck:
Sunday, 3 November 2013
Got as far as the hide on the Swale NNR
I thought I got as many as 15 White-fronted Geese, Anser albifrons, feeding in front of the hide, together with about 50 Greylags and a dozen or so Black-bellied Brent Geese, Branta bernicla bernicla. This time I was sure that there were a mix of adult and juvenile birds. Also a sparrowhawk I think, and a grey heron. On the fenceline behind there were about 50 Goldfinches fluttering about. Half a dozen swans and cygnets were scattered around, and a couple of white (farmyard?) geese.
Saturday, 2 November 2013
Lightning visit to Muswell Manor Beach and the Brent Geese
On the way I thought I picked out a Mediterranean Gull from a dispersed group of Black-headed Gulls on the fields on the Leysdown Road before the planted wood. I stopped to have a peek at the Raptor Mound, and there was a probable female Marsh Harrier over the reed-bad of the Capel Fleet.
On the beach there were numerous Black-headed and Herring Gulls, together with a few Greater Black-backed Gulls. There were also Oystercatchers, Redshank, a couple of Godwits, and a Curlew.
But the birds I had really come to see, the Dark-bellied Brent Geese, Branta bernicla bernicla, from the Russian North Artic were also there, in small groups of half a dozen or more. They are said to breed mainly on the Taymyr Peninsula in the far, far North. They winter in the South East of England (50% of the World population), and France and Holland, and in the spring they gather in the WaddenSee and then migrate further North and East via stopping off sites particularly such as the White Sea and the Kanin peninsula, heading for the Taymyr peninsula, travelling thousands of miles altogether.
The white neck flashes on the necks, and the dark bellies, only a bit less dark than their uppersides, were clear, and the white rears showed well. All of the ones that I saw looked like adults. The number of young, I seem to remember, may perhaps be partly dependent on the number of lemmings, and the resulting predation choices by Artic Foxes. They are certainly quite inconsistent breeders year on year.
The population dropped drastically in the 30s through to the 50s, recovered into the 70s, and stabilised in the 90s, at about a quarter of a million birds.
The Brent Goose population is generally protected in Western Europe under the EU Birds Directive 79/409 and under various national legislation. Hunting is not currently permitted, except in some local regions. As a result of the recovery and further increase of population size, however, proposals have been made in some countries for a regulated harvest of Brent Geese.
The Brent Goose is a success story in modern conservation; as a result of protection on the wintering grounds, together with other factors such as feeding on agricultural land and the recovery of eelgrass beds, they recovered from a very low population level in the 1950s.
On the beach there were numerous Black-headed and Herring Gulls, together with a few Greater Black-backed Gulls. There were also Oystercatchers, Redshank, a couple of Godwits, and a Curlew.
But the birds I had really come to see, the Dark-bellied Brent Geese, Branta bernicla bernicla, from the Russian North Artic were also there, in small groups of half a dozen or more. They are said to breed mainly on the Taymyr Peninsula in the far, far North. They winter in the South East of England (50% of the World population), and France and Holland, and in the spring they gather in the WaddenSee and then migrate further North and East via stopping off sites particularly such as the White Sea and the Kanin peninsula, heading for the Taymyr peninsula, travelling thousands of miles altogether.
The white neck flashes on the necks, and the dark bellies, only a bit less dark than their uppersides, were clear, and the white rears showed well. All of the ones that I saw looked like adults. The number of young, I seem to remember, may perhaps be partly dependent on the number of lemmings, and the resulting predation choices by Artic Foxes. They are certainly quite inconsistent breeders year on year.
The population dropped drastically in the 30s through to the 50s, recovered into the 70s, and stabilised in the 90s, at about a quarter of a million birds.
The Brent Goose population is generally protected in Western Europe under the EU Birds Directive 79/409 and under various national legislation. Hunting is not currently permitted, except in some local regions. As a result of the recovery and further increase of population size, however, proposals have been made in some countries for a regulated harvest of Brent Geese.
The Brent Goose is a success story in modern conservation; as a result of protection on the wintering grounds, together with other factors such as feeding on agricultural land and the recovery of eelgrass beds, they recovered from a very low population level in the 1950s.
Saturday, 19 January 2013
Barden Lake
Greylag Goose, Anser anser, Only a few were on the lake today, but I think the main flock may still have been nearby. At one point I heard them on the neighbouring fishing lake.
This cob mute swan has a rather strange looking tip to its beak, and I think it must have suffered a rather traumatic wound to the lower bill and tip:
A very unusually coloured coot has been around for a couple of days, flocking with all the other waterfowl, including many "normal" coots, near the feeding area.
Just one of the two Egyptian Geese were seen today, which unfortunately I think we disturbed so that it flew off over the lake. It appears to have been eating the grass around the lake.
A drake tufted duck looks seriously at me!
This looks like an adult Black Headed Gull, Chroicocephalus ridibundus, just starting to replace its winter plumage with its brown headcap. As it darkens it tends to look sooty black rather than the brown of the fully developed cap - as do the winter head stripes. I have never seen any explanation of this. The bill is also already darkening up, showing less of a distinction between a redder base and a darker tip. By the time of the breeding season, the bill is often sufficiently dark overall to be almost concolorous with the headcap. This picture shows the very clear "white eyelid" effect
This next must be an immature Black Headed Gull, first winter perhaps. The most obvious feature are the dark-centred tertials, very clear in this individual. Tertials are apparently not true flight feathers but are located on the upper arm, near the body, and are used primarily to cover the primaries and secondaries while at rest. The so called tertial step is an important ID feature in some gull species while at rest - see this blog reference. Note also the orange base to the bill, characteristic it seems to me of overwintering first years and juveniles in general. It is a bit puzzling as there is little in the way of brown along the side of the wing - its all mainly at the back of the wing - but there is so much of it that I think it must still be a first winter. You can also see the dark tip to the tail, if only just, from this angle.
I think this is a different bird, from the other side of the lake taken much earlier, and a slightly worse photograph. However it's a very similar pattern of brown on the wing:
This is a rather more conventionally coloured wing, on a bird on a signpost stuck in the middle of the lake by the main (Western) feeding area, Again note the orangey rather than reddish bill (and legs?) of these young birds:
And another one from the Western side, again with some browning along the wing, although perhaps not quite so much as the previous picture. The small dark smudge to the front of the eye visible in most wintering birds is fairly obvious in this picture:
And here is the one Common Gull, Larus canus I saw, just before I was distracted by a "hooded" Black Headed Gull, and so I only confirmed it for sure when I looked at the photos later.
This is a drake Mallard, Anas platyrhynchos. The Mallard were in small groups across the lake today, but some at least appear to be pairing up.
There were a couple of cormorants, Phalocrocorax carbo, on the lake, diving for quite long periods and distances, so presumably fishing. One took off from the water and flew low across in front of one of the two islands, and the blurry photographs showed the white thigh patch of an adult in the breeding season.
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