Autumn songs

Despite the days becoming shorter and darker, a few birds are still singing. Robins, both males and females claim their winter territories with their heartfelt, melancholic song, Wrens can be prompted to go on their outburst of song all year round, often by other bird calls and Starlings, donning their brightly spotty winter plumage call enthusiastically from chimneys and aerials.

Fledglings galore

The resident birds seem to have synchronised their breeding to such extent that I saw/heard seven different species of fledglings or chicks in my way to work. A Blackbird (#1) fledgling gave a try to hunt for itself, its parents out of sight. It was hilarious to watch it picking up a dried berry and dropping it and listening for worms.

A lovely fluffy Robin (#2) fledgling by the university parking lot, still very naive, let me get quite close (top photo), a pair of Greenfinches landed next to it and had me confused for a while!

Then a pair of noisy rook (#3) youngsters by the university woodland area demanded to be fed, I could only get a poor shot.

The family of Wrens (#4) I pictured a couple of posts ago were still around, the young giving their calls from a bed of nettles and docks opposite the Wilberforce building.

In my way back from work, a lovely family of Long Tailed Tits (#5) 'see-see-seeing', but the young ones shun me and only gave me their tails to photograph.

In my kids school, the Blue Tit (#6) eggs have finally hatched and I watched the live footage, with one of the parents sitting on very hungry and bare chicks

Near home, the Starling (#7) adults and youngsters in the nest have starting calling to each other with their 'churrr' calls which mean that they are almost ready to leave their nests.

Alarmed wrens

A pair of Wrens in the wildlife garden called their rattling alarm calls. I am always intrigued by alarm calls. Many alarm calls are directed to the bird watcher, as we approach a nest or a bird more than it is comfortable with. In this case, the birds were directing their attention to a cat, which was going about its business in the undergrowth. The pair of wrens moved constantly around, chattering nervously. A Goldfinch sat on a branch paying a lot of attention, but keeping quiet. On the top is my best shot of one of the Wrens, and you can see a little video here.

Wren fledglings

I heard some thin calls coming from a thicket in the University Wildlife Area. Two alternating calls, probably coming from two recenlty fledged chicks. Chicks calling alternatively are incredibly difficult to locate as each call makes you look in a different direction. I spotted an adult Wren giving an alarm call nearby and waited. Eventually an adult approached one of the chicks to feed it and I could see where it hid. The chicks were sitting inside some nettles. I could only get a poor shot, but it shows the yellow rim of the mouth typical of chicks.

Builder Wren and counting hens

Wrens start singing early. They have been doing it occasionally since the first days of January, their powerful quick song cheering up the dark winter days. Today they seem to have gone for it on earnest: I heard four different males singing on my way to work. They have lots to do and there is so little, precious time. They have to start building their nests before females are ready to lay. Yes, I said nests, not just one, but many, lots, as many as he can possible make before the females start visiting. And also, I said females, as wrens are polygynous, with one male mating with between one to nine females per season. Each spring, male Wrens, Troglodytes troglodytes, build several nests in their territory in quick succession. They are called "cock nests" and are spherical, with a side entrance, placed in suitable locations and offer the structure of the finished nest (the female will line it with hair and feathers). It takes between half a day to five days to make a nest. Although Wren's songs are incredible powerful for their minute size it is the nests the females will judge before settling for a male, in particular, the number of nests. The male will display to entice the female to each vacant nest, singing and excitedly guiding her to the nests, to advertise what an accomplished builder he is. The more empty nests a female is shown the better. The next graph shows the positive relationship between the number of nests built by a male and the number of females making breeding attempts - and therefore the number of fledglings that the male will sire.

(from Evans and Burn, 1996)

 Males vary in their ability to make nests - or in their ability to defend a territory where the nests can be built. Age makes a difference, with older males better at making nests. Habitat structure is also important, with denser vegetation indicating a better territory, where nests are less likely to be predated. But the most important explanatory factor is male condition: heavier males at the beginning of the season will be able to make more nests, so the number of nests is a measure of male quality. Females benefit from mating with males demonstrating their good condition, so it pays them to carry out a nest count before settling for a male. Experimental manipulating of number of nests present on each male's territory carried out by Mathew Evans and Joe Burn showed that the actual number of nests is the mate-choice cue that the female uses to assess male quality. The making of multiple nest by the male wren as an ornament, an extended phenotype result of the same factor than the tail of the peacock, a signal of quality selected by sexual selection.

References
Evans, M. (1997). Nest building signals male condition rather than age in wrens Animal Behaviour, 53 (4), 749-755 DOI: 10.1006/anbe.1996.0311


Evans, M., & Burn, J. (1996). An experimental analysis of mate choice in the wren: a monomorphic, polygynous passerine Behavioral Ecology, 7 (1), 101-108 DOI: 10.1093/beheco/7.1.101