Pinkfeet together

At East Park this morning we came across a Greylag flock by the cafe lawns. I spotted the Pinkfoot, and then another, which surprised me. There has been a resident Pink-footed goose in East Park for a year now, a young bird flocking with Greylags. In November, I had spotted a different bird (and blogged about it, see here), also with Greylags at Pearson Park. Could these be these two birds that had got together?
 I looked carefully at my photos and saw that they have distinct bill markings, one with a very small mark close to the nail, the other with a larger U shape mark. The older bird, with the U shape mark (I'll call her Stripe) appears to the the East Park resident. The younger bird, still with tiny body feathers has a small bill patch and matches the bill marks - and tiny white feathers around its bill - of the one that was at Pearson Park. Despite being younger, this bird was bigger and has a larger head, with a Roman profile and a thicker neck and a heavier head, so it might be well a male. Since last saw both birds I was impressed how much more grown up they look. Their neck stripes are better delineated, their head shapes less gentle, and they have a more silvery backs as they have moulted their juvenile feathers. The Pinkfeet stayed near each other in the flock, but one lunged at the other when it got too close. At some point the flock got wary of a radio controlled car, and after a crescendo of cackles, they flew off.

'Dot' Pearson Park 20/11/2014

East Park, today. A male?

'Stripe' East Park 14/2/2014

East Park, today, a female?

Dot's juvenile feathers very noticeable in the flanks, with some adult feathers, darker and silvery just over his legs.

Stripe seems to have a full adult plumage now.

In the wrong flock

Although I wouldn't consider Pink-footed Goose (also known as Pinkfoot) to be an urban bird, it is a species that I regularly see. Skeins of this migratory geese, announced by a chorus of high pitched calls, regularly fly over the city in October and March, on their way to and from their breeding headquarters in Iceland and Greenland. Occasionally, however, a straggler will turns up with Greylags in local parks, allowing a closer look.
  On my way to work, walking through the park, a flock of Canada Geese and another of Greylag geese were about. While counting them I noticed a much smaller goose, a Pinkfoot, amongst the greylags. They have small bills, marked with pink, much darker head, contrasting with the slaty back. I think this individual was a young bird born this past summer, as you can see two types of feathers in its flanks and back, as the larger adult feathers, with a pale edge, have started to grow. The furrows that adorn the neck of adult geese are not yet sharply defined. The goose wasn't welcome and was often lunged at by the Greylags. Surprisingly, it was quite relaxed in the park, despite proximity to people, and it got very close to me as it followed the other geese across the lake and then to the grass to feed.
 I other occasions when had previously seen other Pinkfoot with greylags, it was also young birds. I wonder if leaving with your own species as the flock departs takes some learning. Geese need to reach a consensus before leaving as a flock, a decision that takes place by increasingly noisy vocalisations and movements of the birds of the flock when they are ready to leave. If a young bird misses the cues, it will fail to take off might miss the flock altogether, becoming stranded possibly with another geese species. Geese have long lives and move about, so most likely, while following the greylag flock in its travels, it will eventually meet a Pinkfoot flock and the young bird will be reunited with other members of its species.

A Greylag drives the pinkfoot away from its partner

Walking towards the grass. The difference in size between both species is evident here.

Canada Geese taking off decisions

This morning, the 60 strong flock of Canada Geese that seemed to have roosted in the park were restless. There were continuous loud grunts and honks and, after a crescendo in which more and more individuals joined in the calling, part of the flock took off in a coordinated way. The vocalising geese were making a decision, with individuals deciding to join or not a party leading the departure, maybe to quieter feeding grounds. It is unclear if the individuals felt hungry or if the several dog walkers had made then nervous (or both!).
  Flocking birds have to travel together to stay in a group to search for new feeding or roosting patches, to avoid predation or to migrate. When the individuals differ in their motivations to move away (some might be hungrier than others, for example), there might be a period in which an a consensus is reached about leaving or staying involving communication of the individuals intentions. An individual that is not hungry might change its mind and join in if most of the flock appear willing to move, so as not to become isolated.
  Dennis Raveling, in a paper in 1969, reported on the behaviour before flock taking off in Canada Geese. He observed a large flock in their natural range, in which 77 geese had been marked and radio tracked, including 10 families. Flock departure was preceded by a ceremony, with the neck stretched, there are quick head tossing movements with the bill pointing up and repeatedly, and the white head patch conspicuously displayed - communicating an intention to fly. Geese often spread and flap their wings and start to walk in the intended direction of flight for a few steps (this video illustrate this behavior). Ganders (adult male geese) were more successful at recruiting his family than any other family members, as a shorted time elapsed from his initiation of head-tossing until the family took flight, although all family members initiated head tossing at some point. In a couple of occasions when an excited immature took flight but the rest of the family did not follow, it flew in a circle and returned with the family shortly.
 Other than the cohesive function of the head-toss ceremony for family members, group vocalisations and wing flapping serves to synchronise the whole flock. The coordination of the flock during take off included the presence of an invisible 'starting line': individuals run until they arrived at the same position at which the individual before them had just taken off (instead of taking off where they were). Raveling hypothesized that the contrast between the white tail coverts and the black tail served as a signal to optimise the position of individuals during flight, quite important in such large birds. Families tended to keep together during flight and their vocalisations then changed from grunting to a more trumpet-like honking.

More information

Dennis G. Raveling (1969). Preflight and Flight Behavior of Canada Geese The Auk, 86, 671-681 DOI: 10.2307/4083454

Goldfinches and dandelions

You don't need to get out much to enjoy wildlife. Literally, sometimes surprising things happen right at your doorstep. This morning I had to stop short of opening my front door as I realised a pair of goldfinches were standing next to it. One of them was grabbing a couple of dandelion heads - that had probably tumbled over with its weight - and feeding on the unripe seeds. This went on for quite a while. The photographs were taken through glass.

Goldfinches are specialist on small seeds, they benefit greatly from flocking when foraging as they need a lot of effort to obtain enough biomass from tiny seeds that have to be prepared and swallowed one by one and they can devote less time to scanning for predators when they are in a flock.

Gluck investigated these effects on Goldfinches feeding in orchards in Germany during the breeding season. He recorded Goldfinches feeding on milky ripe seeds from 20 plant species. Of these, most of his observations were on five species: Dactylis glomerata (Gramineae), Knautia arvensis (Dipsacaeeae), Senecio vulgaris, Taraxacum officinale and Tragopogon

pratensis (Compositae). The following graph illustrates the relationship between the number of dandelion seeds ingested per minute and flock size in Goldfinches, showing that even in small flocks of 5 birds each bird can almost double their seed intake per minute.

I am a big fan of dandelions and today's sighting is going to make me do even less weeding around the garden.

More information

Erich Glück (1986) Flock size and habitat-dependent food and energy intake of foraging Goldfinches. Oecologia, 71:149-155.