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Thorny topics

‘Domestic’ Mallard, Rutland; compared with the typical bird behind, note the different patterns on breast, neck and around the tail coverts

In recent years a growing body of work on the genetic structure of Mallard populations has been undertaken (see links below). For Britain, Soderquist et al. (2017) found: Signs of admixed farmed mallards were found among wild mallards from the Faroe Islands, Germany, Great Britain, Iran, and the Netherlands, but their genetic origin could not be ascertained, because there were no farmed mallards available for reference from these countries. Nevertheless, admixture in Germany and Great Britain could result from the annual releases of 100,000 and 500,000 farmed mallards in these two countries, respectively.

The male in the photograph is not a hybrid, nor is it one of the recognised domestic breeds. The most likely explanation is that it has some genes from domestic stock. Some domestic Mallards are obvious, but others are more subtle. It would be interesting to know more about the proportion of ‘wild’ birds which now carry ‘domestic’ genes. For further details about the research, see:

https://www.researchgate.net/publication/321398118_Admixture_between_released_and_wild_game_birds_a_changing_genetic_landscape_in_European_mallards_Anas_platyrhynchos
https://www.orn.mpg.de/3379727/Genetic_changes_during_the_farming_of_wild_mallards_and_the_introgression_of_altered_genotypes_into_the_wild_population

Another view of the same bird

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Canada x Greylag (foreground) with Canada Goose, Notts.

Some of our most familiar hybrid geese are the offspring of feral Canada and Greylag Geese. The appearance of these birds is reasonably consistent, though there is some variation and some disagreement over the significance of a dark bill (for example, does it betray Swan Goose ancestry?). My own view is that some Canada x Greylag hybrids are dark-billed, like the one below. At least, that seems the most economical explanation of their appearance. Note that hybrids involving domestic geese of mixed ancestry are more varied.

Further images and discussion can be found at:

http://www.gobirding.eu/Photos/GreylagGoosexCanadaGoose.php
http://birdhybrids.blogspot.co.uk/2014/02/greylag-goose-x-canada-goose.html

Presumed Canada x Greylag, Rutland

Willow Tit, Rutland – when you get a good look the plumage is ‘fluffier’ than that of Marsh Tit

Since my last post I have continued to check former sites for Willow Tit, and so far have found just one pair. Despite claims to the contrary, and overlap in most characters, Marsh and Willow Tits are not normally difficult to identify in the field. Marsh is still reasonably numerous, gregarious and conspicuous. Normally the ‘pitchu’ call is heard before birds are seen. Willow is often more retiring, sometimes found along old hedgerows in out of the way places, but again the ‘eez eez eez’ call is normally heard first; pale panels in wing and tail are striking even at moderate range.

Whilst searching the countryside I have found pairs of Ravens throughout Rutland, yet many farmland birds have declined sharply. This is not news, but when you can spend several hours and see just one Yellowhammer something is wrong. Continuous crops and lines of flailed hedgerows leave them little room. The occasional small areas of setaside are like giving loose change to urban beggars: wholly inadequate to solve the problem.

Occasional highlights have included another Nordic Jackdaw (so worth checking flocks at the moment), Caspian Gull, more Woodcocks and Chiffchaffs, and this Spotted Sandpiper at Holme Pierrepont (Notts) which I went to see this morning:

Spotted Sandpiper, Notts.

Breeding distribution of Willow Tit in Rutland in 1992 (lower) and 2012 (upper)

As shown by the maps from Terry Mitcham’s Rutland breeding bird atlases (1992 and 2012), the range of Willow Tit in Rutland has contracted significantly. Its current status is worrying, with few recent records. Once breeding birds are known from only a handful of sites, local extinction often follows.

Some of the reasons which have been put forward to explain the decline (e.g. competition and predation) are unconvincing. In terms of habitat, at many former sites there have not been obvious changes. What has changed is a warming climate, reduced availability of invertebrates, and loss of marginal habitats on which Willow Tits are more dependent than species which have shown less sharp declines. It is notable that significant declines have been recorded across Europe, from France to Finland, so the reasons must be far-reaching.

I am hoping to check as many former sites as possible during the next month – if you are lucky enough to find one, please let me know.

Horned Lark, Surrey. Note the pattern of the median coverts, as described by Small 2002. There is some variation, but this feature merits further investigation.

Cold snaps have been interspersed with unseasonally warm weather as winter hurtles towards spring.

Highlights during the past fortnight have included Barn Owls and Hen Harriers on the Lincolnshire Wash, Woodcocks in several local woods, and a Nordic Jackdaw at Horn Mill.

Yesterday was a red letter day. In calm, sunny conditions I began at Staines where the Horned Lark gave good views and called twice (distinctly more ‘throaty’ than Shore Lark). On the way back to Rutland I stopped at Bedford Purlieus, Cambridgeshire, in the early afternoon. As sometimes happens I had nearly completed my circuit and was close to my starting point when whilst watching a group of Marsh Tits I saw a male British Lesser Spotted Woodpecker. They seem to have disappeared from Rutland, and I haven’t seen one for several years, so it was a pleasing find. As an aside, although we can’t prove it, the only Shetland record is very likely to have involved a nominate migrant from Scandinavia/Russia.

I have also begun searching former Rutland sites for Willow Tit, which will be the subject of a future post.

Horned Lark, Surrey. Note the warm, almost rufous, uppertail-coverts.

Welcome to my world: a Canada x Greylag behind four of the subjects of this post at EBR

Previously I posted about a flock of 10 presumed Barnacle x canada hybrids at EBR. Nine remain, and better views over the last couple of days have enabled me to confirm that they are Barnacle x Cackling Goose hybrids. Three more closely resemble Cackling Goose, and one may actually be a Cackling Goose (minima) – see additional images and captions below for more details.

They are unringed, full-winged and wary, but will have come either from a collection in Britain or from feral populations in the Netherlands where Kampe-Persson (2010) commented that “due to mixing and hybridisation with Barnacle Geese the species is hard to count”.

As ever, informed comments will be welcome.

Detail of two of the birds. The one on the right most closely resembles Barnacle, but e.g. the head pattern and upperparts aren’t quite right. The one on the left doesn’t show any features which seem incorrect for Cackling (minima), but given the variation in the rest of the flock I am inclined to be cautious about its identity. 

The hybrid at front resembles Cackling, and even has a small pale crescent on its neck, but note how similar its upperparts are to the hybrids behind and the shadow of Barnacle’s breast pattern (though minima can show something like this). 

Part of the flock in flight

All nine on the water – when swimming they all appear dark-breasted

Part of the flock coming ashore

British Bullfinch, Cambridgeshire

I have posted previously about endemic British taxa (and more will follow); many of them merit further observation and study:

https://rutlandbutterflies.wordpress.com/2014/02/19/red-grouse/
https://birdingontheedge.wordpress.com/2017/06/05/juvenile-shetland-starlings/
https://rutlandbutterflies.wordpress.com/2013/12/28/pine-crossbills/

https://rutlandbutterflies.wordpress.com/2016/11/03/meadow-pipit-revisited/ (now considered monotypic)

Today’s subject is the British Bullfinch pileata. Compared with the nominate Northern Bullfinches pyrrhula which we see on Shetland and occasionally on the east coast, they are reasonably distinctive, being visibly smaller and less brightly coloured; females have browner flanks. The call is less varied, and I have never heard British Bullfinches give the ‘trumpeting’ call which I have heard given by several Northerns.

Bullfinches are remarkable. Despite what may seem a limited vocal repertoire, captive birds have been taught to imitate flutes and whistles. British birds are sedentary, and form durable pair bonds. Unlike Northern birds which have a preference for spruce, British birds are most frequently seen along mature hedgerows. They are currently present in good numbers, so it is a good time to study them.