Thursday, 2 October 2014

Broken Wing

This has been an unusual year for Canada Goose in the park. Usually, a flock visits during the winter, roosting elsewhere and returning every morning to enjoy the bread and food given by people. Some time during last winter, one of the geese got injured, its right wing hanging a bit loose on the side (I first noticed it the 16th of January, the photo above is from the 16th of March). The injury, at the base of the wing, prevented it from flying, and it must have happened in the park, maybe due to a collision with a tree branch or a fight with a dog. The bird seemed content, fed well and recovered enough for the injury to be almost unnoticeable. But when the flock decided it was time to depart for the breeding grounds, at mid February, the lame goose stayed behind. All through the summer it has been alone in the park, joining the mallards during feeding time, and probably roosting on the little island at night. I felt for him as geese are such sociable birds.
Part of the Canada Flock returning from the roost in the morning
 The flock of Canada Geese returned last week. I searched for the lame one in the pond, but failed to spot him, it must have mingled with the rest of the geese. I wished I had been there to watch his reaction to, first, the distant honks of the approaching flock, and then to the geese themselves once they landed. Then a couple of days ago, early in the morning, I spotted him with two others, just before most of the flock returned. Again, today, the goose was with a female before the main flock returned. They followed each other closely, like a pair of geese would do. Could it be that this was/is his partner? Geese form strong partnerships and bond through the year, and for many years if not for life. They also recognise many individuals in their flock, including their past offspring. The female goose is actually staying to roost with the lame goose at night, instead of following the flock. Maybe when the migratory urge kicks in spring she will leave with the flock, but maybe not.
The lame goose in the background, with a partner on the 30th of September
My peak count per visit graph for Canada Goose in Pearson Park. If you try you can see a tiny green bar between week 8 and week 39, corresponding to the lame goose. Created with BirdTrack.

Friday, 13 June 2014

Blue tit family and Sycamore aphids

I heard the rasping begging calls of blue tit fledglings coming from a Sycamore tree, which I find it is a very common occurrence. As I approached I noticed clouds of Sycamore Aphids cascading down from the tree as the adult Blue tits moved about, searching for the aphids themselves and green caterpillars (above). It was a very impressive spectacle as the light hit the aphids and amplified the effect. The tree leaves were thickly peppered with aphids, and fledglings were having a go at finding food by themselves. One of them found a long green caterpillar and wrestled with it for a while until it was able to swallow it.
I tried to capture the density of aphids flying off around the tree in this photo.
The evenly spaced, winged Sycamore aphids (Drepanosiphum platanoidis)
A fledgling begging for food.
The adult cuts the caterpillar in half before feeding the fledgling.
This young one had caught a caterpillar on its own.
You can watch one of the adults foraging and the aphids flying off here.

Friday, 16 May 2014

Offspring recognition in Starlings

ResearchBlogging.org The first Starling fledglings joined their parents in the lawn of the park this morning, running behind their parents begging for food, with a cacophony of calls. Starlings are highly social birds, they like to feed together so the chances are that the still dependent young will join unrelated young while still expecting to be fed by their parents. Starlings have synchronised egg laying so that many young fledge on the same day. While they are at the nest, parents do not need to particularly recognise their offspring individually, as they are likely to be the young in their own nest. However, how can they make sure they recognise their offspring from others so that they feed their own young after they fledge?
  Every year, a week or so before the fledglings leave the nest, adults start using a harsh call 'charr, charr!' (above, listen here) and the by then loud voices of the young can be heard responding from inside the nest. Why, I wondered, do they do this?
 Linda van Elsacker, Rianne Pinxten and Rudolf Frans Verheyen carried out experiments in nest box starling colonies in Antwerp (Belgium), either swapping broods of different ages for a day (Exchange experiment), or offering a choice between their chicks and alien chicks in nearby nests (Choice experiment), or swapping the nest by an empty one and relocating their nest containing young at a certain distance (Search experiment) at different chick ages.
In their choice experiments, carried out when young were 5, 11 and 16 days old, they showed that parents accepted and fed strange chicks until they were 16 days old, as shown by the weight gain of the chicks. In contrast, most parents were able to recognise their chicks when they reached 19 days, ignoring the strange ones completely, and this behaviour was found in all parents when chicks were 20 days old. So by this age adults were able to recognise their chicks.
In the search experiments they showed that the ability of parents to locate their offspring increases quickly and by the time chicks reach fledging age (20-22 days) old 97% of parents searched for and relocated the moved nest containing their young within an hour of the nest having been moved.
 The constant calling by parents and offspring in the days before fledgling might be a way of reinforcing this recognition. So, by the time the offspring are ready to fledge, and then mingle with other chicks, parents are able to recognise their offspring, presumably by their calls.

More information

Frans Verheyen, R., Van Elsacker, L., & Pinxten, R. (1988). Timing of Offspring Recognition in Adult Starlings. Behaviour, 107 (1), 122-130 DOI: 10.1163/156853988X00232

Chaiken, Marthaleah (1992) Individual recognition of nestling distress screams by European starlings (Sturnus vulgaris). Behaviour : 139-150.
Young starling looking for food this morning

...and chasing its parent begging.


Monday, 12 May 2014

Moorhen nest building

The Moorhens seem to have settled in the park, with a pair having secured the island as a territory. Next to the island there is a large fallen branch that has been used to nest before. One of the moorhens was tidying the nest, trying to bring branches sticking up into the nest structure.
 You can watch a short clip of her activities here:

Tuesday, 6 May 2014

Fledglings

In the last couple of days I've come across a number of resident species with fledglings. Blackbirds were first, a short-tailed adventurous chick calling for food in the park, last week (below) and today (above) a Robin yesterday and a Song Thrush and Dunnock today. As the youngsters jump from the nest, they have to face a steep learning curve, they are more or less naive to predators, so in these days between fledgling and independence from parents they need to learn about them and also perfect their foraging skills, usually while they follow their parents, begging.
 Magpies and Carrion Crows start showing an interest on trees and bushes, listening for calling chicks, so the alarm calls of the adults, associated to the different predators are part of the learning process. The first mallard brood in the park has already disappeared, probably due to predation by Herring and Lesser-black backed gulls.
Blackbird fledgling, 29/04/2014, from the same brood as the top photo, today.
These goslings from a local park already show a great interest in people, usual food providers here.
Young Robin
A sleepy Dunnock fledgling
A song thrush finding food for its youngster...
Young Song Thrush fledgling and busy parent.
A Magpie in search of nests or young birds in the undergrowth.
A Herring gull in the park having mallard for breakfast this morning.


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.