Wednesday, 18 January 2017
Friday, 13 January 2017
Sunday, 11 December 2016
Wednesday, 7 December 2016
This morning, I witnessed my second ever 'great Magpie marriage', one or the most puzzling Magpie behaviours. A group of seven magpies (top shot) were high on a tree, calling, a short call, 'chak!' and bowing with wings half spread, displaying, pecking the branches, or chasing around the tree, but mostly watching each other.
This is a short clip of the gathering.
This behaviour, which usually takes place in the winter, in sunny mornings (although it was quite dark and cloudy today) was traditionally interpreted as the way Magpies form pairs before nest building starts. Tim Birkhead, in an article for British Birds, quotes this passage from Darwin's book 'The Descent of Man':
The common magpie (Corvus pica, Linn,), as I have been informed by the Rev. W. Darwin Fox, used to assemble from all parts of Delamere Forest, in order to celebrate the "great magpie marriage." [...] They then had the habit of assembling very early in the spring at particular spots, where they could be seen in flocks, chattering, sometimes fighting, bustling and flying about the trees. The whole affair was evidently considered by the birds as one of the highest importance. Shortly after the meeting they all separated, and were then observed by Mr. Fox and others to be paired for the season.
Birkhead's research with the Magpie population of Rivelin's Valley in Sheffield showed that instead of a pair formation congregation, this behaviour, is instead a territorial challenge by the dominant non-breeding pair. The rest of the flock attend to witness the event and, although the territory owners often keep their territory, in some cases they are ousted by the dominant non-breeders.
Birkhead, T. R. Studies of West Palearctic birds: Magpie 189. British Birds (1989). 82:583-600. Here.
Birkhead, T.R. 1991. The Magpies. The ecology and behaviour of Black-billed and Yellow-billed Magpies. T&AD Poyser, 270 pp.
Thursday, 17 November 2016
The young gull flies off with the freshwater mussel shell.
Later on, with cloudy weather, two gulls handling the shell.
Wednesday, 16 November 2016
In one of my local parks there is a very high density of Crows. There are several territories, but the park is also the main ranging area of the non-breeding flock (where there is also a winter roost). There are a lot of interactions going on, but without ringed birds, it is hard to make sense of what is actually happening. Yesterday, I observed several interesting interactions. First, a Black-headed gull appeared most annoyed with a Carrion Crow and mobbed it repeatedly, dive-bombing on it when the crow tried to stop on an aerial. The crow did not vocalise and deftly avoided the gull attacks. Later, I heard the rattling call of a crow and watched a chase between two crows, one of them calling with the call I usually associate to mobbing a raptor. Crows, it appears, can use this vocalisation to fend off conspecifics.
Finally, I watched a Crow it an amazing display: its head feathers raised, bill pointing down, looking really at its best. After taking a few photos, I realised it's partner was walking nearby using the same posture. Today I learned about this display in 'The Crows' by Franklin Coombs. It is called the 'Bristle head' display. It is a territory-owner display, used in territory boundaries to signal their occupancy, and also aimed at intruders within the territory. Both members of the pair display while they walk about. There is no vocalisation. Territory intrusions mostly occur during the spring, but there is also a peak in October-November.
I can only presume that this pair of crows are a pair ot territory owning breeders. They do look in great shape!
This is a still from a video, which shows both members of the pair with their 'bristle heads'.
A side view of the displaying crow.
This photo is a bit overexposed, but it shows the details and metallic iridescence of the crow really well.