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.

Gulls playing helter skelter?

Do birds play? You have probably seen videos of crows sliding down snow and rolling down on car windscreens, or heard of the Australian black swans that enjoy surfing. These cases, and many others documented for a long time, are hard to explain in utilitarian terms (no feeding, or mating or predator avoidance is involved), it appears purposeless, and seem most fitting to actual play. Play behaviour, often solitary, some times involving objects, but also social, has been described in ten orders of birds including corvids, raptors and parrots amongst others. Some of this behaviour involve play flying, or flying in aerobatic ways. This afternoon, in the first mild sunny day of spring, thermals developed over the park, and a large mixed flock of gulls - Herring, Common, Lesser Black backed and at least a black-headed, later joined by a Carrion Crow - started to soar higher and higher, I could barely see them as they circled. My camera decided to run out of battery run out just at the same time (the photo above is the flock flying high this mid February).
 Then I noticed some gulls tumbling down. Not just gliding, but actually flipping over and going on their backs as they descended. Two of them seemed to be flying together, making a downward double spiral, opposite each other, occasionally tumbling. The Carrion Crow also dropped height by closing its wings as if enjoying the feeling of being kept up by the thermal. It was an exhilarating spectacle to watch, and the gulls gave the impression to be having a good time.

The moorhen nest up the tree

This afternoon I tried and photograph the moorhen's tree nest from a better angle. The nest is located about 4 m high, on a broken branch that is resting on the main fork of the willow. A moorhen was sitting tight on the nest, but only the top of the head and bill was visible (above).
 Its partner kept busy chasing away the visiting coot.

Friday, 20 March 2015

Why did the Moorhen and the Mallards go up a tree?

I occasionally see moorhens on trees. Today one climbed up a weeping willow, then fumbled in a fork that seemed to have a lot of branches in it, before almost right away climbing away on to a clear view of the water and gliding down. A nest? I didn't have a clear view of the moorhen climbing up, it's possible she was carrying nesting material and passing it to its partner? Tonight, I looked at the photos and, yes! you can just see a dark bird sitting on the tree fork. In other photos a bit of bill is visible. A tree nest!
 Then I thought, that's where they have been nesting these past years. The park's lake has little marginal vegetation and the island, which used to have bushes, is now bare as the goose use it for roosting. That explains why moorhen chicks appeared out of nowhere at some point in the year, even when, as last year, they appear to abandon their nest on the island's shore.
This photo shows the location of the nest, on the left hand side.
Preparation to jump onto the water.
I have never before seen a mallard up a tree. This morning, on the grey light of the solar eclipse, a pair of mallard were quite high on a tree. The duck was inspecting the trees, while the drake looked on, appearing quite unsure. They went to two different trees. Apparently, Mallards occasionally nest in hollow trees, their duckling jumping from the height after hatching just like other tree nesting ducks do.
The female is a meter over the drake.
The drake looks on.
So during this day of solar eclipse, I happened upon two birds I don't usually see on trees, doing just that. Not so much the eclipse than spring is in the air and the park doesn't offer the best ground nesting conditions for these birds.

Thursday, 19 March 2015

The Sparrowhawk silence

There are three ways I spot Sparrowhawks. First, during their spring soaring flights, high over their territory, when they are very apparent then, though a bit distant. The second is when Carrion Crows alert me to their presence, when they are mobbing them, chasing them mercilessly while uttering the call that gives the name to this blog: a call that I directly translate in my mind as 'sparrowhawk!'. The third one I have got to call 'the Sparrowhawk silence'. It is an eerie silence just after the synchronic clap of many pairs of wings - Feral pigeons, Gulls - that replaces alarm calls in these birds, and the alarmed calls of Blue Tits or Blackbirds: no gull squabbles, no cooing, no chitchat. If I look up during the 'silence', I am bound to see the brown silent shadow of the hawk, flying low across the trees in the park. I have witnessed this a couple of times this week. Today, when the silence happened I was photographing a Mistle Thrush. It was feeding on a small, but exposed grassy area, but it didn't fly off. It just froze, for maybe two eternal minutes, tense, its tail pressed against the ground, just watching. Afterwards, it relaxed and carried on hunting worms as normal.

Wednesday, 18 March 2015

The Viking gulls

A flock of about 100 common gulls winters in the park, they arrive at the end of September/October and are around most of the time until the end of March. They are very excitable and their squeals provide the background noise of the park in winter, especially when visitors empty their bags of bread by the side of the pond. A cacophony of calls and chases ensues while the gulls pick the bounty fast, before the ducks and geese have the chance to react.
 Is not only bread though for the park gulls, there are very quiet times, especially during the middle of the week, and the gulls will move onto the grass, looking for worms and other invertebrates, watching the ground intently as they walk.
 In wet days they can be seen dancing to entice the worm to the surface of the soil. Like so.
A clip of the behaviour here:

Then they spend some time just flying in circles over the park, in a flock, I am not sure if in preparation to roost, although I am not sure where they spend the night.
A quiet moment in the flock, with preening, snoozing and yawning by the pond.
This is an adult one on winter plumage. Note the yellow bill with faint dark ring near the tip and the yellow legs, and spotty head.
on the 3rd of February this adult looked very nice on the snow, still in winter plumage.
On the 20th of February this adult had an almost white head and a thin red eye ring.
A close up of an adult's head showing mainly yellow bill, red ring. Note the scruffy back of the head, showing the ongoing moult towards a completely white head plumage.

I find them endlessly fascinating and can't stop myself from photographing them, and they are often co-operative, as they are so used to people. When I noted that the flock disappeared each year, one day in March or April I wondered where they would go in the summer, to breed. I need wonder no longer, these gulls come from Bergen, in Norway.
While watching them one day in January I found a couple of Common Gulls with plastic colour rings. I spent some time looking at the legs of many gulls since that day, but I didn't spot any other ringed ones. I managed to get photos where I could read the code and submitted the samples to Euring. I got an e-mail the same day from Morten Helberg with details of their ringing and recoveries. Since then, I have seen the ringed gulls a few times, and managed to get their portraits.
This is J2EX, sex unknown ringed its first autumn (1st calendar year in 2013) which means now should be in its 3rd calendar year (almost adult), although the bill and legs are still grey/bluish and doesn't have a red eye ring or prominent wing 'mirrors'. This is its ringing/recovery history:

15.09 2013 Byparken, Bergen, Hordaland, Norway
17.09 2013 Tveitevannet, Bergen, Hordaland, Norway
20.09 2013 Tveitevannet, Bergen, Hordaland, Norway
21.09 2013 Byparken, Bergen, Hordaland, Norway
14.06 2014 Kilnsea, Humberside, Great Britain
14.01 2015 Pearson park Hull, Humberside, Great Britain (the photo above is from yesterday, also observed 22/01/2015)
This is JV47, Sex male age, 1 cy when ringed last October, so it's in his first winter. He still called like a gull chick when feeding, and adopted this hunched chick posture. Legs and bill base pinkish.
This is it's ringing/recovering history:
05.10 2014 Tveitevannet, Bergen, Hordaland, Norway
(in the month after it was ringed the flock came back to Pearson Park)
14.01 2015 Pearson park Hull, Humberside, Great Britain 

Looking at photos yesterday, I found another ringed common gull, from the 20th of February. It looks like a first winter bird. The code reads JR20. I will update the post when I hear back from Euring.
It is very nice to know where these gulls spend the summer, but something equally rewarding is to know them as individuals. The rings have allowed me to recognised them in my visits to the park. I will look forward to them coming back in years to come, as gulls can be long lived. A typical Common Gull lives for 10 years (the record is 27).

Wednesday, 11 March 2015

Great spotted woodpecker chiselling nest

I heard the 'chip!' call of the woodpecker while walking by the park today. A female flew to the top of a horse chestnut and then flew into the large trees by the side of the pond. When I relocated her she was on the trunk of a large ash, and, as woodpeckers do she climbed behind the trunk out of sight. I moved to a better location, with the sun on my back and there she was, maybe 8-10 m high on the trunk just under the main branches, expanding a hole in what appeared to be healthy wood, pulling woodchips away.
 Woodpeckers will dig a new nest every year, which provides suitable nesting holes for other hole birds. Both male and female work together in this hard task, that might take them three or four weeks to complete.
She worked away while I took photos, and filmed her, and she was still working when I left.
The female on the high branches of a horse chestnut, with buds about to burst

most of the shots I took of chiselling are blurry, but this one captured the moment of impact, and the closed eyes of the woodpecker at this point.

A short clip follows.

Tuesday, 10 March 2015

Stock doves courting

I was lucky this morning to watch a pair of Stock Doves courting from a good vantage point. They usually stick to high branches in the trees in the park, only rarely coming to the ground. Today I heard a male's booming call from the trees opposite the pond, and I climbed to a small hill on the other side. My new camera is heavy and I still need to get used to its weight, so I eventually leaned against a tree trunk to steady myself. The male crouched on a branch bowing parsimoniously at the same time that fanned its tail - very similar to woodpigeon's courtship -, facing the female. Its neck, inflated with air showed while cooing showed its green iridescent neck patch, which looks much larger than when the dove is at rest (bottom photo).
A side view of the male singing
The male looks at the female about to land
She greets her with this lovely display
She eventually lands next to him. This photo is not brilliant, but I like how the neck patch is actually ruffed, something I had not seen before.
More male bowing, fanning tail, showing its iridescent neck patch.
A stock dove at rest, from 27th Feb. Compare the size of the neck path.