Tuesday, 7 April 2015

Coots settling in the park

I wrote about the visiting coot a few posts ago, but there has been new developments in the local park, a few days ago two coots were present and today I counted three coots. They were quite dispersed in and around the pond, but from a particular location all were visible. If they are just coming in or they have been here all along since I saw the first one, I do not know. They are relatively vocal, appearing to keep in touch with each other. This afternoon, two of them seemed quite content, preening close to each other, while surrounded by playing children and lots of people in the park, they most likely dispersed from another park, where they have grown accustomed to people. Male and female Coots have similar appearance, although males are larger and heavier, so possibly the individual in the background, much larger, is a male. Male and female, however, have very distinct calls. I hope that at least a pair stays in the park as they will provide opportunities to get to watch them closely and learn more about their behaviour.
One of the coots being chased away by the resident Moorhen (with its nest in the island tree).
Coot about to dive
This is the third coot, note its very large frontal shield, protruding from the top of the head and stained pink. The two individuals at the top of the post have much smaller shields.

Thursday, 26 March 2015

Forced copulation in mallards

This morning I witnessed a forced gang copulation in mallards. It is a sad thing to watch as the female appears so defenceless, overpowered by a number of males. The female was first pinned down on the ground by three males and a few others joined in later. At least one managed to copulate with her. Forced copulation - as other apparently perplexing behaviours like infanticide - has shifted from being regarded as a pathological behaviour resulting from either captivity, male biased sex ratios or urban bird living, to an sexually selected alternative mating tactic, adaptive for paired males. There are many studies now supporting that forced copulations are more widespread than previously thought amongst some ducks, and are part of their natural behavioural repertoire. (The involvement of many males is probably more likely in urban parks with higher population density than in the wild).
 Mallards form new breeding pairs in the autumn, and the couple stays close together, the male guarding the female. Mating within the pair is very ritualised and brief. There is head pumping by both male and female, the female adopts a flat position and the male mounts her. Here is an example from last week.

 However, occasionally, other males chase a female - often in groups - grasp her and copulate with her forcefully. A feature of this behaviour that made researchers think this might be an adaptive behaviour for males is that forced copulations tend to happen during the period of egg laying, not before egg laying, and rarely after a clutch has been completed. In addition forced copulations tend to happen in the morning, just after the female leaves the nest after laying an egg. The female lays an egg each day, and ovulates just after laying, and it is during this period that there is a small window of time before the albumen is deposited and blocks entrance for sperm that there is a chance for forced copulation to result in fertilisation. The female does not need to be fertilised at this point as she has stored her mate's sperm and therefore she would have fertilised the egg with his sperm. After all, she has chosen this male to be her mate. But the opportunistic males are after fertilising her eggs in this short time window. There is little the female can do to escape the males's attention, she flies away if she can manage, only to be pursued by the males, its male often trying to intervene. I have noticed that males tend to join in chases and forced copulations if they notice a female being chased.
The number of males increased to six at some point. The
 female's bill is just visible towards the right, on the ground.
 Although the female cannot always resist forced copulations, she is not so defenceless after all: her vagina comes to the rescue. What! I hear you say, how? Let me introduce first the fact that ducks are amongst the 3% of bird species that have penises (the right term is pseudopenis or phallus) a corkscrew-like eversible organ, that in the case of the mallard is about 13 cm long (by no means the record, a close relative of the Ruddy duck has the dubious honour).
A screen grab of a male that managed to copulate. Its penis still everted as he walks to the water.
Another view of the male with dangling penis, just after he dismounted.
 Now to the female side. Some female ducks, including the mallard have evolved long, twisted vaginas with dead ends near the cloacal opening, making it harder for a male trying to copulate with her to achieve a successful intromission and fertilise her eggs if she doesn't collaborate. The female's vagina also twists clockwise, making it harder for the male anticlockwise rotating penis to work. The males of these duck species also have longer penises. This co-evolution might have been spurred by forced copulations, in which the females respond to increased penis length with increased vaginal complexity to thwart the likelihood of successful fertilisation. The little data on extra-pair paternity in ducks appears to support this hypothesis, as the occurrence of extra-pair offsprign appears to be quite low (less than 10%) in the ducks studied. An excellent example of an arms race between the sexes.

More information

Brennan, P. L., Prum, R. O., McCracken, K. G., Sorenson, M. D., Wilson, R. E., & Birkhead, T. R. (2007). Coevolution of male and female genital morphology in waterfowl. PLoS one2(5), e418.

Cheng, K. M., Burns, J. T., & McKINNEY, F. R. A. N. K. (1982). Forced copulation in captive mallards (Anas platyrhynchos): II. Temporal factors.Animal Behaviour30(3), 695-699.

McCracken, K. G., Wilson, R. E., McCracken, P. J., &; Johnson, K. P. (2001). Are ducks impressed by drakes' display?. Nature413(6852), 128. here.

The very angry Moorhen

The lake in my local park is now divided up in two Moorhen territories. One pair has the island - now with a nest high in a willow well under construction, possibly already with eggs, the other has the opposite end of the pond, a more disturbed area which only has two patches of marginal vegetation near a path as potential nesting site. One of the island Moorhens climbed the willow tree with some nest material and passed it delicately to its partner sitting on the nest. Both males and females carry out nest building and are virtually indistinguishable by plumage, although males are a bit larger. After a while I saw the moorhen approaching some vegetable refuse that some passer by had dumped on the grass. The moorhen then spied either the other territory owner which was about 5 m away, or the coot that was standing nearby, and carried out the most wonderful display. With the bill quite low and the tail as high as she could keep it, it erected its white tail feathers, and half opened its wings, strutting while showing its bottom to the rival moorhen (which appeared quite indifferent). The view of the rival moorhen approaches the photo at the top. And the front and side views of the displaying moorhen are below.

 You can watch a clip of the behaviour here.

You can also watch the moorhen strutting to a potential predator, a stoat, which I filmed recently here.

Wednesday, 25 March 2015

Snooze time for a Greylag pair

The large wintering Greylag flock in my local park has now disintegrated into pairs, which have moved onto their breeding areas. The last few times the flock was around there were many fights as males started to become very aggressive towards other males. There are now just up to three pairs remaining, sometimes just the one. Yesterday, they were resting with the resident Canada Pair in the lake island where they are less disturbed by dogs and people.
 This pair, is easily recognisable by the male's black bill tip. In ducks, swans and geese the thickened tip of the bill is called a nail. In grey geese, juveniles have a dark nail, while in adults the nail is pale (so I have named this unusual male Black Nail). They are illustrating that paired geese tend to stay close together and do the same things at the same time: rest together, travel together, feed together. Research on the semi-tame Greylag flock established by Konrad Lorenz in Austria, showed that bonded pairs also carry out complementary behaviours, for example males are vigilant while females are foraging or resting. Pairs that had successfully reared offspring together differed from unsuccessful pairs in that they showed more reciprocation: females are vigilant when male feeds more often than in unsuccessful pairs.
  Unlike corvids or parrots, in which mutual grooming is important to keep the pair bond, geese never groom each other, in fact, I don't think I have even seen a pair of geese in actual physical contact (e.g. roosting against each other like pigeons or crows do). Instead, they are social allies, they rely on each other's support against rivals or intruders, and carrying out ritualised triumph ceremonies afterwards. In the Konrad Lorenz flock, although successful and unsuccessful pairs had a similar within-pair distances (keeping within one meter of each other), when previously successful pairs failed a breeding attempt, they remained closer together, showing a tighter social bond.
Eyes open
Eyes half close
In this video you can see an aggressive male chasing away other geese in the flock (taken 27th February 2015).

More information
Scheiber, I. B., Kotrschal, K., Hemetsberger, J., & Weiß, B. M. (Eds.). (2013). The Social Life of Greylag Geese. Cambridge University Press.

Tuesday, 24 March 2015

An encounter with the male Sparrowhawk

This morning a lively chorus of Blue Tits and Chaffinches alerted me to a hunting Sparrowhawk in the park. It flew over and landed on a branch of a Horse Chestnut nearby. Luckily, there was a clear line of sight between the still leafless branches from where I was standing. Its russet underside and small size revealed it was a male. It only sat there for a couple of minutes, scratched its chin, and flew across the road to a willow where I've seen Sparrowhawks sitting before. As it flew, the small birds started calling nervously again. I approached, and managed to find an angle where I could get a clear view. He didn't notice me, instead, he was interested in the birds mobbing him from a safe distance over him, and looked intently.

In the willow, under the cover of its curtain of branches the hawk appeared relaxed. It turned to the sun, raised its feathers and shook them leaving them fluffed out, an action called 'to rouse' amongst falconers (photo below). I was impressed by his long chest and flank heathers, thinly lined with white. Sparrowhawks also have long white undertail coverts, which they fluff out when they display over their territory.
The male turned its back to me again. Every time it changed position, the birds called echoing his movements.
This was the last photo I took from the five minute encounter. Followed by the alarm calls of the small birds, the Sparrowhawk flew away, probably trying to surprise some prey still not alerted to its presence.

Monday, 23 March 2015

The soul thrush

This young male blackbird (recognisable for its brownish wings and black smudges on its bill) sung its beautiful song in front of my house yesterday. Were not for the fact that the blackbird song is so familiar we would herald the blackbird as one of the most pleasant songsters. The song thrush gets the name, but in comparison it's just an apprentice compared to the musical delivery of the blackbird. When I first moved to the UK, my garden's blackbird sung the first notes of Ella Fitzgerald 'Fascinating Rhythm', one of the blackbirds a couple of year back sung 'La Cucaracha' chorus really well. It really deserves the name of the soul thrush.

Sunday, 22 March 2015

Coot diving

We have a visiting Coot in our local park. It is quite used to people and a good photographic subject. Coots dive for a few seconds - they appear to be very buoyant - and lift pieces of vegetation from the bottom, to feed on the surface.

A front view of the coot.
Here is a short video of the coot diving for food.