Fatties

I hadn't expected to do any ringing today but I had planned to go to the baited site at Crawford in the afternoon to top up the feeders.  As I was getting ready to go the wind dropped away completely so I decided to take advantage of the calm conditions and took my ringing gear too. It was 3pm by the time I got to the site and I quickly set up an 18m net after topping up the feeders. There were plenty of Goldfinches and Tree Sparrows around and first birds were caught as I walked away from the net.

A busy little session followed with 27 new birds and 2 retraps caught during the 2 hours the calm conditions lasted. It was interesting that 4 of the 10 Goldfinches caught were very fat and had bulging fat deposits in the tracheal pit and over the abdomen; these birds will be migrants that will be heading much further north and presumably to somewhere in Scotland or Northern Ireland to breed. One of the Blackbirds (a 2cy female) was similarly very fat and weighed a whopping 126.7g. A lean Blackbird weighs around 90g so this bird will have been carrying in the region of 35 to 40g of fat and will be migrating back to Scandinavia or somewhere further east fairly soon.

Female Blackbird

Blowing back the feathers reveals the tracheal pit which is normally deeply concave in a bird that isn't carrying much or any fat but has been completely filled with fat and is bulging in this individual.

This slightly more angled view shows the yellow fat is bulging by several mm and overlaps the pink breast muscles. The abdomen was similarly full of and covered in fat. This bird must be at or very close to the point where it is ready to migrate and it is likely to set off on the next suitable night.

Ivy Berries.
The hedge on one side of the ringing site is full of ivy which is currently covered in ripe berries. These berries help migrant Blackbirds fatten up in readiness for the long journey back to their breeding grounds.

A Blackbird ringed at Crawford in the winter of 2016/17 was caught by ringers on the island of Utsira, off the coast of Norway, in spring last year and gives an indication of where today's fat Blackbird could be heading in the coming days.

Blackbird (Turdus merula)   Ring no: LK25293
Ringing details
First year female   29-NOV-2016   Crawford, near Up Holland Lancashire, England
Finding details
Caught by ringer   29-MAR-2018   Sore Merkeskog, Utsira, Rogaland, Norway
Duration: 485 days Distance: 795 km Direction: 37deg (NE)


Ringing totals (retraps in brackets) for 03/04/2019 were: Collared Dove 1; Coal Tit 1; Song Thrush 1; Blackbird 4; Tree Sparrow 8; Robin 1 (1); Chaffinch (1); Greenfinch 1; Goldfinch 10.