Pied Wagtail winter territories

In the last few weeks, two Pied Wagtails have been feeding around the pond in my local park, staying near each other, but not too close, one chasing the other every now and then. I have watched this before, and managed to get photos last year (top shot, East Park, 9th January 2023). This behaviour, of two Pied Wagtails 'teaming up' to defend a territory during the winter, is quite typical of the species, and it was studied in detail in the early 1980s by Nick Davies and A.I. Houston along the river Thames near Oxford. The feeding territories studied were along the water, on both banks, where the wagtails pick small flies, spiders and beetles often washed onto the mud at the waterline, circuiting along one bank, then the other. The territory owner, usually an adult male, occasionally accepted an intruder as a 'satellite', often a female or juvenile, especially when there were enough resources to share. The satellite appeased the owner with a specific display, with bill and tail pointing up. The owners were more likely to tolerate the satellite when food was more abundant.

Appeasement posture of female White Wagtail (from Zahavi, 1971).

Although the presence of the satellite meant food resources needed to be shared in the territory, the satellite also helped with territory defence. The territories were defended vigorously, as the food resources depleted as the wagtails fed on the washed out insects, so intruders would reduce the feeding rate of the territory holders. Territory defence also involved calls, both of the intruding bird and of the residents. Davies and Houston quantified the benefits and costs of territory defence and accepting a satellite depending on the quantity of available resources.

It is clear that Pied Wagtails have a very flexible social behaviour. They gather in large, compact communal roosts during the night. Also, in places or at times where there is a glut of resources, for example during ploughing time, or emergence of insects, territory defence may break up and the wagtails might gather in loose flocks with little aggression.

In these photos of the East Park pair (above and top shot), the differences in plumage between the male (at the front) and the female behind are apparent.

I couldn't take a photo with both individuals from the 7th December at Pearson park together, but the difference in plumage indicates a male (above)...

... and a juvenile (below) is also clear. Note the juvenile's yellowish face.

More information

Davies, N. B. Food, Flocking and Territorial Behaviour of the Pied Wagtail (Motacilla alba yarrellii Gould) in Winter. J. Anim. Ecol. 45, 235–253 (1976).   

Zahavi, A. The social behavior of the White Wagtail Motacilla alba alba wintering in Israel. Ibis 113, 203–211 (2008).

Waxwing gift passing display

 After a long hiatus, I came across some Waxwings today. Six individuals were perched high up on a Lime tree, taking the sun in. They were quite active, changing branches, pecking the shiny, red tree buds. Two in particular called my attention, as they approached each other touching bills, then coming apart. I took plenty of photos, some unfocused by branches getting in the way, but, looking at them in more detail back at home, I noticed that the two individuals 'billing' were doing more than that, they were exchanging an object, probably one of the tree buds, in a ritual display called 'gift passing' (top shot). The behaviour is seen both in the Bohemian Waxwing, which we get in irruption years in the UK, and in the American Cedar Waxwing. 

The behaviour consist on passing an object, then the individual with the object jumps away, then joins its mate, which 'receives' the object, then the behaviour is repeated and the object passed backwards and forwards repeatedly.

The individual on the left has the gift now.

The individual on the right has it now. Note the raised crests.

Here a Waxwing shows interest in the bright red, shiny buds of the lime tree.

And here, another individual holds some buds in its bill.

I found a description of the behaviour, based on captive individuals and illustrated with photos, which shows that the display is also accompanied from fluffed rump and belly feathers, raised crest and lowered tail, the latest something not very obvious in my photos. The male appears to initiate the behaviour, obtaining the object, and sidling to the female, presenting it. If successful she will accept the object and reciprocate, after jumping away, then close. It is difficult to sex Waxwings, males apparently have longer crests and a more clearly delimited black chin patch.

This is a clip of the behaviour in the Cedar Waxwing, there seems to be a lack of recordings for the Bohemian Waxwing, although the description and my observations fits both species sharing this wonderful display.

More Information

Meaden, F. M. & Harrison, C. J. O. Courtship display in the Waxwing. British Birds 58, 206–208 (1965)

Mistle thrush pairs defending berry trees

Several bird species hold territories during the winter, like Robins or Wrens defending their patch and singing through the winter. It is rarer that a pair will defend a winter territory. I have covered examples like Stonechats and Pied Wagtails before. The former usually include a male and a female, but they are unlikely to be a mated pair.

A pair of Mistle Thrushes near their cotoneaster tree. Northern Cemetery 30/11/21.

Earlier in the week I saw some Rowans heavy with berries along a street. A Mistle Thrush sat on a taller tree nearby. Then another individual flew from the berry tree, a pair! Later in my walk, I saw another pair of Mistle Thrushes near their defended cotoneaster (above). I then realised seen paired Mistle Thrushes in the winter before, near their defended trees. Are they a resident pair? Is a pair better than a single individual defending their berry larders?

             

Clockwise from top left, Yew, Ivy, Rowan and Holly ripe berries.

The berries

Mistle Thrushes are well known for their winter defence of berry resources. Holly is one of the most important defended trees in the UK, followed by Hawthorn, Mistletoe, Yew and, later in the winter, Ivy. At Hull, I've seen Mistle Thrushes defend Holly, Yew, Rowan, Whitebeam and Cotoneaster. Often the same trees are defended year after year.

Mistle Thrush on defended holly, one of an Avenues of Hollies at East Park defended by a pair, 23rd November 2021.

Mistle Thrush overlooking its defenced Rowan, 1st February 2021.

Mistle Thrush on General Cemetery on its defenced Whitebeam at Pearson Park. 17th October 2014.

Mistle Thrush on its defended berry-laden Yew.

A Mistle Thrush atop the church rooftop checks the yew opposite, on Cottingham Road Community Church garden. 14th November 2017.

Defence behaviour

Aggressive tree defence behaviour is spectacular: The Mistle Thrushes use their loud rattling or churring calls, repeatedly and chases other birds away from their tree. Most aggressive interactions involve repelling other Mistle thrushes, but also any other thrushes, like Blackbird, and various finches, Great Spotted Woodpeckers, Waxwings and even single Woodpigeons. Defence consists on chasing intruders, often silently and even if the birds were feeding on fallen berries under the tree. If there is a conflict then the individual might flick its tail and wings, their white underwings flashing, while churring persistently. Churring also occurs in flight during chases. Their defence is effective due to their large body size - they are the largest European thrush. Curiously Barbara and David Snow, who studied this behaviour in the UK note how the Mistle Thrush chooses who to attack carefully and it will chase only some species away so long as they are food competitors for the particular tree it is defending. For example Starlings are left alone in hawthorn and holly (whose berries they rarely eat) but chased from Ivy, which they eat. Greenfinches and Great Tits, are chased from Yew (they feed on the seeds) but not from Holly, which they don't eat. Eventually, after a few attacks, the local birds will learn to avoid the defended trees, and the Mistle Thrush just watches from a distance, and often this is how you'll find a Mistle Thrush, sitting on a vantage point near its precious tree.

Establishment of the guarded tree

Snow and Snow describe that the system of tree defence is established in October or early November, when song might be occasionally heard and other Mistle Thrushes are vigorously driven off until the territory is set. That way they can exclusively feed on these berries through the winter when they are needed. The defended trees become their winter larders, standing out on the landscape, packed full of berries when all other trees have been stripped out. Mistle Thrushes actually avoid feeding on the berries of their defended tree if they can, especially when the weather is mild and the ground is soft and they can rely on worms and other invertebrates. You need to pay attention to these trees full of berries later in the winter to recognise that the reason they are there is that a Mistle Thrush is just sitting atop a tree or aerial nearby, preening or resting. Unfortunately this effort will be worth nothing if a hard weather spell drives flocks of winter thrushes or Waxwings onto their area, then the Mistle Thrushes despite their best efforts may be unable to maintain their tree defence and lose their berry crop in a day or two. If the weather is mild, the tree can hold its berries until spring, and then, usually by the end of March, trees stop being defended. The Mistle Thrushes start nest building, often nearby. In the case of their defence of holly, the long-lasting berries, which can remain in the tree for up to nine months, are often used to feed their young. The hard work of defending the tree through the winter pays off not only to increase adult survival but as parental investment.

A pair of Mistle Thrushes near berry laden rowans at Auckland Avenue, 14th November 2017.

Pair defence

If Mistle thrushes stay to breed on the area near their defended tree, it would make sense that the pair defends the tree, rather than one individual. Snow and Snow describe how pair defence is more common and successful than single individual defence, although no data is given as to the proportion of pair defence. They say that "nearly all trees successfully defended throughout the winter were jointly defended by a pair of Mistle thrushes" and that  “pairs or individuals centred on a source of fruit which, if all goes well, will be defended through the coming winter.” In contrast, research on Mistle Thrushes defending Mistletoe clumps in woodland in Poland did not find evidence of pair defence. Could it be that pair defence occurs in some situations or for some berry sources and not for others? Anecdotal observations, however, suggest that members of a pair can defend different trees in the same area, and join forces if one of the pair loses their tree. On their article on Mistle Thrush defence Barbara and David Snow comment:

"When fruit territories are first established, in autumn, each defended tree may be guarded by a single Mistle Thrush or by a pair. It is probably common for members of a pair to establish themselves at neighbouring fruit-trees. Thus we had three cases where two Mistle Thrushes began by defending separate trees quite near to one another (60-180 m) and later, when one of the trees was stripped (as a result of the onslaught by Fieldfares and Redwings in the severe weather of December 1981), the two jointly defended the tree that still had fruit. In another case a pair of Mistle Thrushes jointly guarded the same holly tree from October or November in the two successive years, continuing throughout the winter in the first year but losing the fruit to invading Fieldfares and Redwings in the second year."

Snow and Snow indeed suggests that the same individuals, if they survive, may defend the same trees year after year, but their birds weren't ringed, so we can't know for sure. I'm surprised there is still so much to known about this widespread bird!

More information
Skórka, P. & Wójcik, J. D. Population Dynamics and Social Behavior of the Mistle Thrush Turdus viscivorus During Winter. Acta Ornithol. 40, 35–42 (2005).

Snow, B. K. & Snow, D. W. Long-term defence of fruit by Mistle Thrushes Turdus viscivorus. Ibis 126, 39–49 (2008).

Snow, B., & Snow, D. (2010). Birds and berries. A&C Black.

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.

House Sparrow

House sparrows have now finished moulting and males are donning their more subdued winter attire. The new feathers have buff fringes that tone down their deep chestnut head and black bib. The bill is also yellowish. This one posed for a few seconds on top of a wire fence before flying away.

Snowy Common Gull

A flock of Common Gulls winters in my local park. Today they have been perfecting their dancing on ice skills as the pond is mostly frozen. They seemed to feel safe on the ice, some of them even sitting for a rest on the ice. This handsome adult one sat nicely for a portrait. I like how snow on the ground makes seagulls look a purer white.

Winter Herring gull pair

The Herring Gull pair at The Rock faithfully return to the park for the winter, and watch developments from their vantage point. I assume it is always the same pair, they stay together and I've never seen more than two at once. Herring Gulls are monogamous, mate for life and live long lives, so the pair might have been visiting the park for years. They are relaxed around people, and, unlike their relatives at the coastal resorts, do not bother people for scraps. They just wait. They know people will bring food to them at the park, no need to beg, just wait patiently.
 Herring gulls are in their winter plumage now, their heads and necks streaked with grey feathers. By February, their head and feathers will be pure white and soon after they won't be as regular in the park, having moved to their summer grounds for breeding.

Spot us

I watched is a local flock of Redwing in a wooded area with clearings. I counted 12, feeding together on the ground, but keeping some distance in a loose flock. They behave very differently to Blackbirds, more wary and watchful, ready to fly silently up to the trees if they are disturbed. One of the birds was feeding amongst leaves, it had dug itself into a hole and enthusiastically pecked leaves aside looking for invertebrates - in very much Blackbird style. Redwings are so cryptic, even when sitting on grass they can pass for a fallen leaf, it's only when you stop and watch that their sudden movements make then apparent. Then you spot not only one, but the ground comes alive revealing the whole flock of Redwings.

Can you see the Redwing?