Loafing gulls

 Gulls spend a good portion of their days doing what is known as 'loafing', in open areas of good visibility: playing fields, beaches, but also on water and on ice in frozen lakes, the same sites are chosen year on year. These loafing areas are different from night roosting sites. At loafing sites gulls appear relaxed: some sleep - head under wing - others sit or stand watching around, others preen. Immatures may play with objects such as sticks or leaves. Loafing areas are common areas, and tend to be quiet, with little or no squabbling or aggressive behaviour, often with several species mixing in the same area. Individuals come and go, commuting to their feeding areas, unless a disturbance provokes a sudden communal flight. On the coast, the number of individuals in a loafing area follows a tidal cycle - as low tides expose food resources the gulls move away the loafing area to feed- and also time of the year. Tidal influence in sleeping is highly prevalent in wading birds, which strongly depend on exposed shores for feeding. A study in Herring Gulls suggest that they have a dual sleeping pattern, with the proportion of sleeping gulls peaking at midnight and at midday. This may be a common pattern with urban gulls or away from the coast, where food is less related to tidal fluctuations.

A mixed flock of Black-headed gulls, Common Gulls and Herring gulls loafing on a rise on a local park.

Loafing gulls allow good opportunities to check individuals for plastic rings, as shown by this preening Common Gull.

A group of Common Gulls loafing on ice on a frozen pond of (16/1/2013)

More information
Shandelle M. Henson, James L. Hayward, Christina M. Burden, Clara J. Logan and Joseph G. Galusha. 2004. Predicting Dynamics of Aggregate Loafing Behavior in Glaucous-Winged Gulls (Larus glaucescens) at a Washington Colony. Auk 121, 380–390.

Cooke, F. and Ross, R. K. 1972. Diurnal and Seasonal Activities of a Post-Breeding Population of Gulls in Southeastern Ontario. Wilson Bull. 84, 164–172.

Galusha, J. G., JR and Amlaner, C. J., JR. 2008. The effects of diurnal and tidal periodicities in the numbers and activities of Herring Gulls, Larus argentatus, in a colony. Ibis 120, 322–328.

Wintering Chiffchaffs

In the last month, I've come across a couple of wintering Chiffchaffs. The last of them this Wednesday on my way to work, the calling bird revealed it's presence atop a maple, busily feeding on the top branches. Although most UK warblers are breeding migrants, four species can be found during winter. Two of these are resident species, the Dartford and Cetti's Warblers. The situation is more complex with the Blackcap, which I've covered before, and the Chiffchaff.

Sewage plants and wetlands
Chiffchaffs are insectivorous year round, so they can't rely on garden feeding like Blackcaps during winter. Overwintering in Chiffchaffs was documented in the early 19th century, but this seem to involve very few birds. In recent decades, however, there seem to have been an increase in numbers, possibly aided by global warming. Ringing and recaptures have allowed estimates of around 100 individuals gathering in suitable sites. Chiffchaff winter survival depends on a steady supply of invertebrates (mainly midges, gnats and aphids) and sheltered sites where to roost. They appear to survive several consecutive nights with frost, so the increased temperatures may have more important effects on insect abundance, not actual survival of the birds. Suitable habitats include sheltered coastal areas, but they also use urban and suburban sites, especially near water, sewage treatment plants (where warmer water means an abundance of insects) woodlands and hedgerows. The Chiffchaff on the top shot, fed low on the marginal vegetation around an urban lake, East Park, Hull on 2/12/2013.

It's complicated...
The Chiffchaff is part of a species complex and its taxonomy has changed quite a lot in recent years. What was considered a single species now includes the Canarian and Iberian Chiffchaff, previously races now elevated to species level. The Chiffchaff proper is now divided into various races: the nominal race, collybita, breeds in the UK, whereas tristis or Siberian Chiffchaff, and Scandinavian Chiffchaff abietinus. The three races are very similar, differing in the tone of the plumage and subtle morphological features, and more notably, song and calls. Given this and the occurrence of intermediate forms between some of the species makes them very difficult to identify in the field.

Residents, migrants and winter visitors
It appears that the bulk of the UK breeding population of Chiffchaffs, belonging to the subspecies collybita, migrate south in the winter. In addition, there is very strong passage through the UK, especially in the autumn, mainly of northern European birds moving to winter quarters in the Iberian Peninsula, and Northern and Western Africa and these include a sprinkling of abietinus and tristis individuals. What about the winter birds? Where do they come from?

Ringing and DNA analysis
Ringing recaptures in the winter don't include locally breeding Chiffchaffs, suggesting that the winter birds are also migrants. Most of them appear to belong to the collybita subspecies, which breeds in western Europe and Southern Scandinavia. Recoveries of birds ringed in winter in Southern England have been made subsequently in N England and Denmank during the breeding season. Recently, DNA analysis has come to the rescue. It is possible to obtain enough material for DNA analysis from tiny feathers, dislodged when ringing birds. Sending these feathers for DNA analysis allows to discriminate between subspecies, as they have distinct DNA. Individuals captured in the south of England include some Siberian chiffchaffs confirmed by DNA. Over 20% of ringed wintering Chiffchaffs in a mixed woodland by a lough in Ireland was confirmed to be tristis and two individuals were confirmed as abietinus. So it appears that wintering Chiffchaffs include individuals from all three European subspecies, that once finding suitable locations during migration they settle for a while to feed. Ringing recaptures have found the same individuals wintering repeated years in the same location. Another intriguing feature of wintering Chiffchaffs is that males, which are larger than females, were the bulk of wintering chiffchaffs in the past, although females are increasingly wintering. There is still so much to learn on Chiffchaff migration, taxonomy and evolution.

More information

Clement, P. 1995. The Chiffchaff. Hamlyn Species Guides. pp126.

Clement, P., Helbig, A. J. and Small, B. 1998. Taxonomy and identification of chiffchaffs in the Western Palearctic. Br. Birds 91, 361–375.

Birds in Cheshire and the Wirral. A breeding and wintering atlas. Wintering Chiffchaffs. 

O’Mahony, B., Farrer, D. and Collinson, M. 2008. Genetic identity of wintering Common Chiffchaffs Phylloscopus collybita trapped in County Kerry in 2015. Ir. Birds 

Ray Meads Ringing Group A review of our wintering chiffchaffs.
Simms, E. 1985. British Warblers. The New Naturalist Series. Collins. 432 pp.

What are goldfinches doing on tree branches?

At this time of year I often see Goldfinches appearing to feed high on tree branches, often sycamores. It is hard to see what exactly they are doing, but definitely there are no seeds involved, it looks like they are pecking the bark or possibly lichens. I checked and they were not holding seeds under their feet (as they often do) or wiping their bills clean. They appear to peck the surface of the branch. I managed to photograph one that appears to lift and hold a bit of bark with lichen on top (top shot).

I am very curious to know what they are doing. During the breeding season Goldfinches use lichen to camouflage their nests, I only see this behaviour during winter. Has anyone seen this? Please comment! Some more photos of the behaviour follow.

3/12/2017.

25/01/2018

25/01/2018. This individual stayed pecking the end of this branch for quite a while.

16/11/2016

UPDATE 11/1/20
I found out a chorusing Goldfinch flock in a local park today. Several of them were feeding on branches in two lime trees. I managed a couple of videos showing how they target areas at the end of broken branches and deftly peel bark and wood, discarding bits. If they are feeding on the bark or wood itself or on some invertebrates living in it is unclear.

Mute Swan acoustic communication

I've said it before, Mute Swans are not really mute, they have a repertoire of calls and sounds. They also use movements of their head and neck to communicate. There is a quick head bowing movement, and a courting movement in which the feathers at the top half of the neck are ruffled, while those at the bottom are not, while the swan bows his head alternatively to left and right; and the aggressive 'busking stance' of the territorial male. In this post I focus on sound communication. I have trawled through Xenocanto, an encyclopaedic website with thousands of bird calls, to compile the following selection of Mute Swan sounds. I was prompted to write the post after listening to an odd distant call, which I didn't recognise to start with, and I was surprised to find out that it was a mute swan's. I heard the call again today, young swans calling to a swan flying overhead. It is not straightforward to distill the 'meaning' of a call, but the context can helps.

1. Snort

A short grunt or snort, often uttered when the swans are relaxed, and appears as a contact call while feeding, between members of a family, but also a greeting call. A lone young swan snorted when I walked by a lake near him.

2. Begging call

A soft repeated whistle typical call of young. Mute Swans don't 'feed' their young by putting food in their bills, but they help the young to obtain their food by paddling with their feet to  disturb the sediments or by pulling underwater plants. Even fully grown immature swans carry on whistling.

  3. Wing-beat Sound

This loud sound produced by the mute swan's wing-beats is really eery, especially when it takes you unawares until you realise that is coming from a swan. It carries very well and appears to replace the trumpeting contact calls of other swans.

4. Hissing

An aggressive sound, usually uttered by the female she has small young and a danger (human, dog) approaches. The bill is open and the swan adopts an upright stance towards the danger source.

5. Contact all

A two-note contact call reminiscent of other swan's flight call. I heard this call when a pair was separated, maybe during landing (one ended up in the river, the other one in a lake). Also when a Mute Swan flew over a family, the juveniles used this distance call.

6. Courtship calls

A range of snorts and grunts during courtship.

 Have I missed any? Let me know in the comments.