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).