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| Male Brambling with Goldfinch through the double glazing |
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| Female Chaffinch (l) and Brambling (r) on the lawn |
Showing posts with label Brambling. Show all posts
Showing posts with label Brambling. Show all posts
Saturday, 16 March 2013
Back garden Bramblings
Thursday, 20 December 2012
Bunch of finches
Thought that it was about time I put some seed out for the birds last Friday. Already the finch numbers have risen from approximately zero to 2 Brambling, 4 Greenfinch, 6 Goldfinch, 2 Bullfinch and about 15 Chaffinch. Not a bad return so far... I was particularly pleased with the Bramblings which only visited fleetingly last winter but were both feeding on the sunflower hearts today.
The photo is of very poor quality but just about shows both Bramblings on the right of this group of Chaffinches.
The photo is of very poor quality but just about shows both Bramblings on the right of this group of Chaffinches.
Sunday, 20 February 2011
Garden finches
The 'real birding' has yet again failed to materialise this weekend, so like the birds I have been foraging for scraps in the garden. Luckily the scraps were definitely worth feasting on – a nice healthy selection of finches at the feeders. The hide has been a very successful, if somewhat unconventional, piece of suburban garden furniture. I'm not quite sure what the neighbours think of it!...
First up, one of at least nine Bramblings that have been drawn in to the baited area. I hope that some of the males hang around for a few more weeks so that they have a chance to wear away those pale fringes to their head and mantle feathers.
After a very slow start, the niger feeder has been increasing in popularity. Only a single Goldfinch has visited as yet, but with at least three others in the area I am hoping it is only a matter of time before the whole charm descends.
Lesser Redpolls are the most frequent niger feeders. At least three have been on the feeder at any one time, with another six or so on the ground beneath. No sign this weekend of last week's Mealy Redpolls. They clearly do not realise that I set up the hide for them!
The Lesser Redpolls seem to be pretty regular now and one of the males has taken to singing from the birch tree. Not quite full song-flighting, but a good start for February. Here he sorting out his tail feathers in between bouts of singing. This undertail is at the pale end of the spectrum for this form, but Lesser Redpoll he is.
Another species that has been feeding in the garden this weekend is the Siskin. Just this individual so far, but with another dozen or so in the trees nearby, surely it is only a matter of time before there are swarms of them on the feeders.
Finally, the Chaffinch, a species that has kept a remarkably low profile this weekend. Here is male and female photographed yesterday by the youngest in the family - well done!
First up, one of at least nine Bramblings that have been drawn in to the baited area. I hope that some of the males hang around for a few more weeks so that they have a chance to wear away those pale fringes to their head and mantle feathers.
The Lesser Redpolls seem to be pretty regular now and one of the males has taken to singing from the birch tree. Not quite full song-flighting, but a good start for February. Here he sorting out his tail feathers in between bouts of singing. This undertail is at the pale end of the spectrum for this form, but Lesser Redpoll he is.
Another species that has been feeding in the garden this weekend is the Siskin. Just this individual so far, but with another dozen or so in the trees nearby, surely it is only a matter of time before there are swarms of them on the feeders.
Finally, the Chaffinch, a species that has kept a remarkably low profile this weekend. Here is male and female photographed yesterday by the youngest in the family - well done!Saturday, 8 January 2011
Superb winter birds: siskins, brambling and waxwings
After bemoaning the lack of cooperation of carduelid finches this week, I was treated to prolonged close views of a swarm of stunning Eurasian Siskins today. With a strong sun on a fresh snowfall I headed for the Hermitage of Braid this morning. I had seen a large flock of siskins earlier in the week in the young alder trees planted as part of the urban forest project. Hoping to find some redpolls in the area, instead I ended up surrounded by literally hundreds of beautiful siskins.
See previous post to see what happened next to the bird below?
There were plenty of other birds around and I was pleased to add White-throated Dipper and Eurasian Woodcock to the year list at the Hermitage. No sign of the Common Snipe in their usual area, nor of the Water Rail that turned up in the same spot this time last year.
Birdlife around the house was also noteworthy today with at least 13 Brambing in amongst the House Sparrows and Greenfinches first thing this morning until flushed by a Sparrowhawk. Later on a couple of Bohemian Waxwings dropped in to the back garden. This was thoughtful of them as that's a species that can easily become a gap in the yearlist as the year moves on...
There were plenty of other birds around and I was pleased to add White-throated Dipper and Eurasian Woodcock to the year list at the Hermitage. No sign of the Common Snipe in their usual area, nor of the Water Rail that turned up in the same spot this time last year.
Birdlife around the house was also noteworthy today with at least 13 Brambing in amongst the House Sparrows and Greenfinches first thing this morning until flushed by a Sparrowhawk. Later on a couple of Bohemian Waxwings dropped in to the back garden. This was thoughtful of them as that's a species that can easily become a gap in the yearlist as the year moves on...
Friday, 17 December 2010
Feather de-pigmentation in Carrion Crow
I had to drop the car off at the garage this morning - the windscreen washer motor has gone, which is not too clever at this time of year. Never mind, life is just a stream of birding opportunities, and I set off walking home on foot with my SLR over my shoulder. Within minutes a dozen or so Waxwings had appeared, though too brief and distant for pictures. In addition, six Tree Sparrows at the entrance to Blackford Glen tripled my highest previous count for this area. These birds along with Fieldfares and Bramblings in this suburban setting, provided further evidence of the effects of hard weather movements in response to the bitterly cold northerly airflow we have just experienced.
A Carrion Crow was feeding at the road side. True to form and notwithstanding the severity of the weather, it was instantly spooked by the sight of a human showing any interest in itself, so it hurried off. As it flew it revealed that it was one of those crows that have white patches of feathering in the wings.
This form of plumage occurs regularly in Carrion Crows and birds like these feature regularly in on-line identification forums such as Bird Form. In fact, by strange coincidence one appeared there today (referring to the American Crow, but the plumage aberration is one and the same). Admittedly it can be quite an exciting plumage variation, especially when it forms a full double white bar across all of the flight feathers. I saw a double white wing-barred crow when I was at school in the 1980s and sincerely thought I had stumbled upon something very rare indeed...
Usually this plumage in crows is described as leucism, a term that is used widely for plumage lacking in, or reduced in, pigmentation. The Oystercatcher on the right (photographed at Musselburgh Lagoons, East Lothian, 26 May 2009), for example, shows much reduction in its melanin pigments with the black feathers replaced by a mixture of white and fawn plumage.
Melanin adds to the strength of the feather structure. As a result black feathers are more resistant to wear (and maybe bacterial degradation) compared to white feathers. This additional strength afforded by the dark melanin pigments possibly explains the regular occurence of black wingtips in many different species of birds. Conversely, as the less resistant pale fringes of many feathers are worn away, the appearance of a bird's plumage may change without the need to moult. Certainly, the paler patches of these odd Carrion Crow's plumage often appear to be suffering heavily from the effects of abrasion.
However, I do not think that these areas of feather de-pigmentation have the same origin as either the overall leucism shown in the Oystercatcher above or in the individual white feathers that show up regularly in species sucha s the Blackbird. These aberrations are likely to be due to the switching on or off of particular genes in the cells responsible for feather development. Instead, in the crows it is likely that this plumage aberration is a symptom of a dietary deficiency. The scarcity or absence of a particular nutrient, or precursor substrate, is preventing sufficient successful completion of the metabolic pathway generating melanin. The tail of the Carrion Crow pictured above certainly appears to show growth bars that indicate some variability in health or dietary status during the period those tail feathers were grown (given the uniformity of the bar, presumably this is a 1CY bird that grew all of these feathers at the same time?).
So what evidence is there that this plumage aberration may be the result of a dietary deficiency:
Calcium deficiency is cited as being the cause of this plumage by at least some bird rescue centres (and here). Crows that are severely affected by this condition grow normal plumage at their next moult once given an appropriate diet. Whether there is evidence for the deficiency being due to a lack of calcium is unclear, but this appears to be strong evidence that this plumage aberration has an environmental cause and is not solely under genetic control.
Folic acid deficiency has been found to cause feather de-pigmentation in domestic chickens. The feather producing tissues originate from neural crest cells and folic acid is known to affect neural crest cell differentiation. Of course, crows are distantly related to chickens, so some metabolic pathways may be different, but there is a very strong link between this plumage aberration and environment.
In addition, it is interesting that viral infection can lead to this symmetrical feather depigmentation:
Circovirus infection evidence has been found in Australian Ravens with this these white patches their wings. In this case the feathers also had thickened sheaths which did not allow the correct development and opening out of the feathers. It is possible that our crows are also affected by a similar circovirus and that this is an underlying cause of the white patches we see in our birds. Again, this evidence from Australia strongly supports the idea that an environmental agent can be a key factor in the development of this aberrant plumage.
It is worth noting that there is no evidence that this plumage aberration is a solely inherited characteristic. Instead, it seems reasonable to conclude that it is likely that an environmental factor (e.g. diet or viral agent) is a determining factor influencing whether the correct melanin development occurs in the wing feathers of crows. It may be that feather de-pigmentation is a better term than leucism for this type of aberration, though, of course, it is unlikely to catch on...
A Carrion Crow was feeding at the road side. True to form and notwithstanding the severity of the weather, it was instantly spooked by the sight of a human showing any interest in itself, so it hurried off. As it flew it revealed that it was one of those crows that have white patches of feathering in the wings.
This form of plumage occurs regularly in Carrion Crows and birds like these feature regularly in on-line identification forums such as Bird Form. In fact, by strange coincidence one appeared there today (referring to the American Crow, but the plumage aberration is one and the same). Admittedly it can be quite an exciting plumage variation, especially when it forms a full double white bar across all of the flight feathers. I saw a double white wing-barred crow when I was at school in the 1980s and sincerely thought I had stumbled upon something very rare indeed... 
Usually this plumage in crows is described as leucism, a term that is used widely for plumage lacking in, or reduced in, pigmentation. The Oystercatcher on the right (photographed at Musselburgh Lagoons, East Lothian, 26 May 2009), for example, shows much reduction in its melanin pigments with the black feathers replaced by a mixture of white and fawn plumage.Melanin adds to the strength of the feather structure. As a result black feathers are more resistant to wear (and maybe bacterial degradation) compared to white feathers. This additional strength afforded by the dark melanin pigments possibly explains the regular occurence of black wingtips in many different species of birds. Conversely, as the less resistant pale fringes of many feathers are worn away, the appearance of a bird's plumage may change without the need to moult. Certainly, the paler patches of these odd Carrion Crow's plumage often appear to be suffering heavily from the effects of abrasion.
However, I do not think that these areas of feather de-pigmentation have the same origin as either the overall leucism shown in the Oystercatcher above or in the individual white feathers that show up regularly in species sucha s the Blackbird. These aberrations are likely to be due to the switching on or off of particular genes in the cells responsible for feather development. Instead, in the crows it is likely that this plumage aberration is a symptom of a dietary deficiency. The scarcity or absence of a particular nutrient, or precursor substrate, is preventing sufficient successful completion of the metabolic pathway generating melanin. The tail of the Carrion Crow pictured above certainly appears to show growth bars that indicate some variability in health or dietary status during the period those tail feathers were grown (given the uniformity of the bar, presumably this is a 1CY bird that grew all of these feathers at the same time?).
So what evidence is there that this plumage aberration may be the result of a dietary deficiency:
Calcium deficiency is cited as being the cause of this plumage by at least some bird rescue centres (and here). Crows that are severely affected by this condition grow normal plumage at their next moult once given an appropriate diet. Whether there is evidence for the deficiency being due to a lack of calcium is unclear, but this appears to be strong evidence that this plumage aberration has an environmental cause and is not solely under genetic control.
Folic acid deficiency has been found to cause feather de-pigmentation in domestic chickens. The feather producing tissues originate from neural crest cells and folic acid is known to affect neural crest cell differentiation. Of course, crows are distantly related to chickens, so some metabolic pathways may be different, but there is a very strong link between this plumage aberration and environment.
In addition, it is interesting that viral infection can lead to this symmetrical feather depigmentation:
Circovirus infection evidence has been found in Australian Ravens with this these white patches their wings. In this case the feathers also had thickened sheaths which did not allow the correct development and opening out of the feathers. It is possible that our crows are also affected by a similar circovirus and that this is an underlying cause of the white patches we see in our birds. Again, this evidence from Australia strongly supports the idea that an environmental agent can be a key factor in the development of this aberrant plumage.
It is worth noting that there is no evidence that this plumage aberration is a solely inherited characteristic. Instead, it seems reasonable to conclude that it is likely that an environmental factor (e.g. diet or viral agent) is a determining factor influencing whether the correct melanin development occurs in the wing feathers of crows. It may be that feather de-pigmentation is a better term than leucism for this type of aberration, though, of course, it is unlikely to catch on...
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