Thursday, 17 April 2014

Mistle thrush collecting nesting material

The resident pair of mistle thrushes rattled while flying to the lawns in the park. One of them fed on worms for a while taking little notice of me, but then it found a feather and seemed to have a change of heart, as it started to collect nest lining material enthusiastically, and then it flew to a large horse chestnut rapidly growing its leaves.

A flock of Lesser Black-backed gulls

It is unusual to have more than a pair of Lesser Black-backed gulls in my local park. Today, I counted six circling over the pond in the morning to feed on scraps. They shared the pond with a few young of last year and and adult Herring gulls and a single common gull. After eating some bread, two individuals went to the water to drink.
 These are really beautiful gulls, with the most stern looks due to their deeply seated yellow eyes circled by a red eye ring. The individual at the top was particularly stunning, its red spot was really bright and extended extending to the top side of the bill, like some badly applied lipstick.
 Here, Lesser Black-backed gulls are summer birds, from March to August, and presumably breed atop buildings locally.
Four of the Lesser black-backed gulls
Lesser Black back gull on the water
A pair by the water. Note the darkish ring on the top of the bill, indicating these have recently adquired their adult plumage (about 5 yr old). Note also the different tone of the yellow legs.

Wednesday, 16 April 2014

Carrion Crow begging to its partner

A Carrion Crow collected food in its bill and gular pouch on the University playing fields. Sitting in the nest atop a still bare ash, its mate called repeatedly, a begging, hoarse, nasal call, kaaaa! similar to a Rook's. The crow collecting food - most likely the male - looked up to the nest and flew heavily upwards in circles, stopping on a roof on the way. The female called again and flew off the nest to meet him, calling like a fledgling would do, crouching and wing flapping. The begging and feeding carried on out of sight on the roof.
In Carrion Crows, the female incubates and is fed by the male during this time, so it is likely that the nest on the ash tree already has eggs.
male crow collecting food for its mate

The female returns to sit on the nest (maybe already has eggs?)
The female's tail sticks up from the nest.

Monday, 14 April 2014

Great tit holding seed

A Great tit holds a seed that just fetched from a bird table. Tits in general are dextrous birds, and often manipulate seeds or fruits before consumption. There are many passerine birds that hold food with their feet, from a total of 20 families in a revision on the topic by George Clark. Other examples include Carrion Crow, Rook, Siskin, Goldfinch and Crossbill.

More information

Clark, G. A. (1973). Holding food with the feet in passerines. Bird-Banding, 91-99. here.

Saturday, 12 April 2014

Summer and winter Blackcaps and evolution

ResearchBlogging.orgDuring April, Blackcaps return to thickets and woodland, where the male's beautiful song joins the resident birds. These Blackcaps have just arrived from their winter quarters in Spain and North and coastal West Africa. We tend to think of migration behaviour as something fixed, but recent research shows that many birds have recently changed their migration routes. One of these is the Blackcap.
In the last 50 years or so, a small contingent of Blackcaps have started to winter in the UK. About 30% of gardens have a wintering Blackcap in recent years. Is it because these birds are staying here year round? Surprisingly not, they are migrants from the continent, mostly from Germany, where they breed. This migration behaviour has evolved in a few generations, with these birds taking advantage of milder winters, increased food availability in gardens and a shorter migration route. They usually migrate to Britain and Ireland as winter berry and winter temperatures drop at the beginning of the year. The direction in which blackcaps prefer to migrate is innate, strongly influenced by one or a few genes: the offspring of blackcaps migrating NW prefers to migrate NW, and the offspring of hybrids between NW and SE migrants have an intermediate migratory direction. Birds with both migration strategies coexist in South Germany and Austria. The different migration routes mean that they arrive at their breeding grounds at different times, and therefore tend to pair with birds with a matching migration strategy. The birds involved in the shorter Germany-UK migration trips have evolved shorter, more rounded wings than the Mediterranean migrants. In addition, they have slightly different plumage colour, with might also help them find the right mate. Bill shape is also different, possibly reflecting a different diet: birds wintering in the Mediterranean feed mostly on fruit, while British wintering birds rely mostly on fat and seeds in gardens. These differences are reflected in incipient genetic differentiation between blackcaps with different migration routes present in the same area during the breeding season, which could mean that both populations eventually become different species.
A wintering female Blackcap feeding in my garden. 26/1/2013.
A summer migrant male singing today.
More information
Rolshausen, G., Segelbacher, G., Hobson, K., and Schaefer, H. (2009). Contemporary Evolution of Reproductive Isolation and Phenotypic Divergence in Sympatry along a Migratory Divide Current Biology, 19 (24), 2097-2101 DOI: 10.1016/j.cub.2009.10.061
Fiedler, W. (2003). Recent changes in migratory behaviour of birds: A compilation of field observations and ringing data Avian migration, Springer Berlin Heidelberg., 21-38 DOI: 10.1007/978-3-662-05957-9_2

Friday, 11 April 2014

Discoloured crow

A carrion crow waited patiently to eat some scraps on the verge until walkers passed by. I noticed the pale patches on its wing and tail feathers. This is no mutant, it is a bird that has grown its feathers while fed on poor quality food. According to van Gouw:
Partly coloured feathers are very unusual in leucism. Individual feathers that are partly coloured usually indicate a bad condition of the bird during feather growth and is not an inherit- able character (ie, is not leucism). This is often seen in, eg, Carrion Crows, especially those eating junk food in cities.
Blackbirds with white feathers on their heads or bodies are leucistic. You can see one in this post. Leucism is an inherited trait distinct from albinism, when animals are unable to produce melanin (a black pigment) at all on their bodies, resulting on all white individuals with red eyes. This doesn't affect carotenoid (yellow, red, orange) pigments, so these colours are unaffected if the normal bird displays them, e.g. an albino blackbird will have a yellow/orange bill (see an example here).

More information
van Grouw, H. (2006) Not every white bird is an albino: sense and nonsense about colour aberrations in birds. Dutch Birding, 28(2), 79-89. here.

Thursday, 10 April 2014

Dunnock portrait

This male Dunnock made a pause in between bouts of singing. He looks pretty dapper sitting on the spruce branches, almost smiling to the camera.

Thursday, 3 April 2014

Blackbird singing by first pear blossom

In the last few days, all the resident blackbirds have started singing regularly. We pass through a few territories on our way back home from school playing 'who can spot the singing blackbird'. This one was sitting quite low on a front garden, with the beautiful first pear blossom opening around him.