Sunday, 28 June 2015

Sunbathing Blackbirds

With  long spells of strong sunshine dominating yesterday's weather I wasn't surprised to see a Blackbird sunbathing on the lawn in the afternoon. However, what was a surprise was seeing five sunbathing at the same time with 4 of them close together on the lawn. The sunbathing was interspersed by bouts of preening and birds repositioning themselves to get the best of the sun's rays. Also, there was some coming and going amongst the birds that meant there was a minimum of six different birds involved and there could have been as many as eight. This is the first time I have seen so many Blackbirds sunbathing together and there was clearly a social element to the behaviour with birds choosing to sunbathe in close proximity to each other.

It was interesting that 2 adult females settled down to sunbathe so close to each other. They were joined by a juvenile soon after as can be seen in the next photograph.

With a mini heatwave forecast for next week there will be a lot more opportunities for the garden Blackbirds to indulge in more communal sunbathing.

Tuesday, 23 June 2015

Crawford 23/06/15

The number of birds using the feeders at Crawford has been growing judging by the speed they have been emptying and I have had to fill them every other day just to keep pace. I don't normally carry on feeding such sites into summer but the potential to catch good numbers of Lesser Redpolls , Goldfinches and Tree Sparrows has tempted me to do so.

The forecast for this morning was near perfect so I decided to go and put up a couple of nets for a few hours. I opted for a leisurely start rather than getting up a stupid o'clock and arrived just after 6:30 a.m. I soon had the nets up and started catching straight away and it was clear that a good number of juveniles were now using the feeders. The first couple of hours were quite busy but the catching rate then slowed as the sun burned off the cloud cover and made the nets more visible. I packed up by 10 a.m. having caught 59 birds comprised of 44 new birds and 15 retraps.

Juvenile Lesser Redpoll
Juvenile Goldfinch
Juvenile Tree Sparrow
Ringing totals (retraps/controls in brackets) were: Goldfinch 15 (6); Lesser Redpoll 4 (3); Greenfinch 5; Chaffinch 1 (1); Bullfinch 1; Tree Sparrow 10; Great Tit 1; Long-tailed Tit 1 (1); Blackbird 1 (1); Robin 1; Dunnock 2 (1); Magpie 1; Chiffchaff 1. Juveniles made up just over half the catch with a total of 30 and included 9 Goldfinch, 8 Tree Sparrow and 3 Lesser Redpoll.

A few new adult Goldfinches were caught and provided more examples of variation in plumage. Both of these birds are males (age code 6) with the bird on the right having a less extensive red mask than some females.
This female Chaffinch had a quite a bad a case of scaly leg which is caused by an infection of mites. This bird was released unringed because of the severe encrustations. Chaffinches seem to be particularly prone to this condition and infected birds are encountered fairly regularly.

Saturday, 20 June 2015

Sexing Goldfinches: easier said than done.

My previous posts on this subject are still attracting a lot of interest and my original photographic guide (link here) has been viewed thousands of times. When I put that guide together I was dealing with birds that had been caught in autumn and winter and consequently were not of known sex. However, that post illustrated the problems that can be encountered when trying to sex birds from the extent of the red mask, appearance of the lesser coverts and the colour of the nasal hairs. Around a third of the birds couldn't be sexed on plumage with a sufficient degree of certainty as they had one or more feature that was intermediate in appearance or they had what appeared to be contradictory plumage features.

I managed to catch a few birds last summer that I was able to sex from the presence of a brood patch in the case of females or a cloacal protuberance in the case of males. Although the sample size was quite small they threw a bit more light on the plumage features and on the extent of the red mask in particular. These birds confirmed that there is an overlap in the extent of the red mask between males and females and perhaps far more than is generally realised.

Bringing matters up to date I have caught more Goldfinches so far this breeding season than I have ever done before and I have been able to confirm the sex of these birds by checking them for the presence of a brood patch (female) or a cloacal protuberance (male). Being able to handle and photograph more birds of known sex has confirmed that there is a significant degree of overlap in the appearance of some males and females and others are what might be considered borderline. So lets have a look at some of these recent birds.

Z414635 was retrapped and photographed on 16/06/15                   Z414932 was ringed on 16/06/15                   
Z414933 was ringed on  16/06/15                                       Z414934 was ringed on 16/06/15    
Z414921 ringed and photographed 12/06/15.                   Z414888  retrapped and photographed 12/06/15  
The images above show 6 of the 13 adult Goldfinches that have been caught on my last two visits to Crawford. These birds are broadly similar in appearance but having said that there are some differences in the extent of the red mask with Z414934 (middle right) having the most extensive and Z414921 (lower left) having the least extensive, both above and below the eye. All have some greyish or greyish white nasal hairs or greyish feathers at the front of the crown except for Z414934 (middle right). Some readers of this post may be happy to suggest the sex of some or all of these birds and there is certainly no harm in giving it a go. They represent almost half of the birds caught recently so they are not unusual examples by any means.

So what sex are they: well Z414635 and Z414932 (top left & right) are females and both had very good brood patches; Z414933 and Z414934 (middle left & right) are males and each had a bulbous cloaca; Z414921 (bottom left) is a male and also had a bulbous cloaca while Z414888 (botton right) is another female that had a very good brood patch. Had I caught these birds outside the breeding season I would have probably left several unsexed based on the extent of the red mask and colour of the nasal hairs. In fact  Z414635 (top left) was originally ringed on 18/01/15 and I left it unsexed at the time and that was using all the plumage features including the appearance of the lesser coverts. However, I did make a note that I thought it was possibly a male so it was a really useful to retrap this bird and find out that it is a female and that I nearly got it wrong. 

The other feature that is usually checked when using plumage to sex Goldfinches is the appearance of the lesser coverts. The images below show the lesser coverts of the birds above and in the same order.

female                                                                                   female    
male                                                                            male      
male                                                                                               female
Some ringers don't have much confidence in the appearance of the lesser coverts when it comes to sexing Goldfinches but I think they are just as useful as the extent of the red mask. The image of the lesser coverts that stands out to me is female Z414735 (top left) which is quite unusual as it has mainly black lesser coverts with very little in the way of brown fringes. I have never seen a female Goldfinch with so little brown in the lesser coverts before and that, in combination with the extent of the red mask, is why I even thought it may be a male when it was originally ringed in January. The other birds more or less conform to the general rule that females have mainly brown lesser coverts or very broadly tipped brown lesser coverts while those of males are black or mainly black with well defined and usually narrow brown fringes although Z414934 (middle right) has quite broad brown fringes for a male but they are really well defined. It is worth noting that the black portion of the lesser coverts is usually deeper black and glossier in males than it is in females but as with all Goldfinch plumage features there is some overlap.

There is one more confirmed sex bird that I should show in this post to illustrate another variation in the lesser coverts. I used photos of this bird (D954944) in a recent post because it was a control and I mentioned its appearance then. The bird is a male but it had lesser coverts that looked more female like. However, the lesser coverts were mainly a golden-yellow or broadly tipped golden-yellow rather than the usual brown. It was originally ringed on 09/11/14 as an adult but wasn't sexed at that time. I can only assume the unusual appearance of its lesser coverts played a part in the decision not to sex it when it was ringed. Some may see examples like this as a reason to treat the lesser coverts as an unreliable feature but I simply see it as another variation to be aware of.

Male Goldfinch D954944 photographed 27/05/15
I would love to be able to say that I have found a reliable way of sexing all Goldfinches from their plumage but unfortunately I can't. The more I look at the plumage of birds that have had their sex confirmed by other means the more overlap in the plumage features I see. It is far too easy to get overconfident when trying to sex Goldfinches from their plumage and I know I have been guilty of that in the past. I can't give a definitive figure for the proportion of birds that can't be safely sexed on plumage alone as the time of year will make a difference. Autumn birds present more problems than late winter birds as the protracted moult of the head feathers can make a difference to the appearance of the extent of the red and nasal hairs. Whatever the figure is it is likely to be significant and it could be as high as 30%.

Whatever your view is on this subject I hope you find the photographs of known sex birds useful at least. Some blogs and guides only show images of males and females that have very obvious differences in appearance similar to those below. Those birds are not the problem and simply making reference to the variability of the species doesn't show the points of overlap where accurate sexing starts to become more difficult or impossible using the plumage features discussed. I hope this post has gone some way to rectifying that.

I know it is obvious but Z192897 on the left is a male and D725790 on the right is a female. These images are similar to those that are often shown and described in sexing guides but they don't tell the whole story as they are not typical examples of most males and females.

Wednesday, 10 June 2015

Starling RAS round-up.

My Starling RAS (Retrapping Adults for Survival) period has ended but the project continues with the ringing of adults and juveniles outside the main study period. The juveniles are being ringed to look at both dispersal and future recruitment into the breeding population and the later adults are being ringed to see if they are recorded in the main study period in future years. It may not sound the most exciting of projects but the more I have got to know my Starlings the more interesting they have become.

I have caught and colour-ringed or re-sighted nearly all of adult Starlings that have visited the garden since mid-April and the total currently stands at 160 individuals, which is far more than I had originally anticipated. Interestingly 60 of these adults were ringed in previous years with the 4 oldest retraps having been ringed in 2011. Next year should be even more interesting as the proportion of retraps should be much higher now that the majority of adults breeding in the area have been ringed.

The first juvenile was caught in the garden on 22nd May and a total of 154 have been ringed since then. It is hard to say if Starlings have a had a good breeding season from the number of juveniles caught in the garden but I suspect productivity may be down on last year. On the plus side the majority of juveniles have been good weights so at least they have got off to a good start even if overall productivity is down.

Some other species seem to be having a really dreadful breeding season and although the weather has warmed up during the day it is still quite cold overnight. There just aren't enough insects around and birds that mainly rear their young on caterpillars are having a particularly tough time. The numbers of moths and other insect attracted to the moth trap are still only a tiny fraction of what they should be at this time of year so it doesn't look like the situation is going to improve any time soon. It wouldn't surprise me if this breeding season turns out to be one of the worst on record for some species.