Mallards are notorious for their unorthodox sexual practices, which include same sex mating and necrophilia (of Ignobel Prize fame, see reference below). This morning, in the apparent absence of a female, four drakes mallards took it on an unfortunate one. I have previously watched apparently consensual male-male copulation in mallard, preceded by courtship, but in this case they behaved exactly like when a gang of males carry out a forced copulation on a female. The series is not very clear, but these are the best I got.
...and the harassed drake eventually flew off!
I do wonder if the many non reproductive pairs and trios that are now found away from water around the verges of the avenues and even on campus, where there is no pond, are actually seeking some peace and quiet from all this pond sexual excitement.
More information
Moeliker, C. W. The first case of homosexual necrophilia in the mallard Anas platyrhynchos (Aves: Anatidae). Deinsea 8 (2001): 243-247. here.
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 one, 2(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 Behaviour, 30(3), 695-699. McCracken, K. G., Wilson, R. E., McCracken, P. J., &; Johnson, K. P. (2001). Are ducks impressed by drakes' display?. Nature, 413(6852), 128. here.
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.
The drake mallards at the park have now almost completely finished their summer moult and are sporting their dazzling fresh plumage. Mallards start the breeding season quite early. The first stage is pair formation, which starts in September-October. Any unpaired females attract the attention of drakes and a flock of suitors surrounds her, parading. A trademark display of many ducks is the 'grunt-whistle'. In mallards this consists of a sequence of behaviours including a whistle, at the same time that the duck lifts both his head and tail.
The fact that there are usually many males displaying at once and any of them can carry out the behaviour, means that I've had trouble recording in it a photo previously. By the time I head a whistle, or several, I have missed the behaviour. This week in the park, when I noticed the mallards courting, I decided to focus on a particular male and try and catch him doing it.
The first step of the grunt-whistle sequence looks like the duck is about to dive. Instead, he arches his head forward forcefully, and his bill tip scoops an arc of water droplets toward the female. I managed to get two shots of this stage. The second shows the droplets quite well.
Then is the whistle, while lifting the tail and head (note the bill is a little open).
After that, the drake turns to the female (top shot), and then swims fast with head forward, almost touching the water.
I will try and get a video of the whole sequence in the next few weeks and upload it here.
More information
Wolfgang M. Schleidt & Erhard Oeser (2011) Konrad Lorenz’s use of cinematic film for studying dabbling duck courtship behaviour and the availability of historic film materials. Wildfowl 61: 45–51. Here.
Although I used this photo in my other blog, I thought it is fitting here too. A drake Mallard in the park that didn't flinch and rested while I took his photo.
Yawning is known to be contagious in primates, but having a good bath is something birds often will do in company. As soon as one starts, others nearby, often of the same species, will copy. Bathing washes and cleans feathers, and afterwards, the bird dries up by shaking tail, wings, body and head and then proceeds to oils the feathers by spreading over them a secretion produced by a gland above its tail. A few days ago, I watched these Mallards bathing and preening in sequence with some enthusiasm, today it was some Great Black Backed Gulls, the Sparrows in my garden often do it as well.
Male Mallards have good reason to keep their feathers in top condition, as they will be already paired or looking for a partner at this time of year. Maybe bathing is also an opportunity for showing off.
This is probably one of the most familiar duck behaviours. Mallards often 'upend' to feed, submerging the anterior parts of their bodies and keeping their tails pointing up, while keeping their balance paddling with their feet - a behaviour most kids find hilarious. Although it is not a universal duck feeding method, Mallards are amongst the experts. Mallards are dabbling ducks, they obtain most of their food from near the surface. Upending allows them to reach just a little bit deeper and feed at depths not used by smaller dabbling ducks but too shallow for diving ducks. In contrast to smaller dabbling ducks, mallards and other large dabbling ducks can afford to upend as their large size allows them to reach deeper and to remain submerged for longer.
Proportion of Mallards feeding using different feeding methods (from Green, 1998).
In a comparative study of duck feeding behaviour, Andy Green found out that neck dipping and upending were the predominant feeding methods in Mallards. Ferruginous ducks, a species of diving duck, did not upend and barely used the neck dip, diving was overwhelmingly the most commonly used method.
You can watch Mallards upending in this short video:
More information
Andy J. Green (1998). Comparative feeding behaviour and niche organisation in a Mediterranean duck community Canadian Journal of Zoology, 76, 500-507 : 10.1139/z97-221
There are just a handful of female mallards in the local park pond. Today I could only see a couple. As for males, there must have been at least two dozen around. This male skewed sex ratio seems to be a general phenomenon in the mallard, possibly due to a higher female mortality during migration and incubation, but given the time of the year, many females in the park are probably already incubating. The remaining females are followed everywhere by their zealous males. Many bird species form monogamous pairs, which help each other in raising the offspring. This is called 'social monogamy' but genetic analysis revealed that it does not follow that the social pair are the parents of the offspring they are raising. First, male cuckolding occurs with some regularity in many species, so that the female mates with other males and a proportion of the offspring is not fathered by her social mate. Secondly, females occasionally carry out 'egg dumping' on other pairs nests.
Mallard pair mounting in the autumn
In the case of the Mallard, our commonest duck, there is social monogamy, with pairing observed at least for six months of the year and lasting at least several years. Pairing starts after the moult in the autumn, when even pair displays and mounting are common, even though breeding cannot occur. Males do not share the parental duties, the female being in charge of incubating, brooding, leading the ducklings and keeping them out of danger. Pairs can be seen carrying out a ritualised courtship, but a different mating strategy is commonly seen, in which one or several males chase a female and force her to copulate.
Group of drakes attempting copulation with a female
Females do try to escape these attempts by flying, diving or hiding and call loudly - presumably for their partner - and they are known to have been injured or even drowned in the process, probably due to the number of males trying to hold onto the females neck to secure copulation. In most cases females are not injured - other than losing some neck feathers - and forced copulations can result in fathered offspring, so it is in the interest of the drake to guard the female against this 'extra-pair' copulations to ensure that he fathers as much offspring as possible. Drakes maintain very close proximity to their mates during a critical period, - up to four days before the beginning of egg laying and up to four days afterwards - following the females everywhere. Males only swam away from their partners to chase other males away or initiate fights when other males approached his partner. Males also attempted to stop forced copulations on their partner with varied success. But it was also during the critical period that both paired and unpaired males initiated approaches to paired females. If the female was on its own, she called loudly if other males approached. Mate guarding also benefits females allowing them to forage more efficiently and possibly, decreasing their mortality due to predation because of their mate's alert state. Males with high testosterone levels in spring are more efficient guarding their females, and females show a preference to pair with such males during the autumn.
More reading
Cunningham, Emma J. A. (2003) Female mate preferences and subsequent resistance to copulation in the mallard. Behav. Ecol. 14: 326-333. here.
Davis, Ellen S. (2002) Female choice and the benefits of mate guarding by male mallards. Animal Behaviour, 64: 619-628. here.
Goodburn, S. F. (1994) Mate Guarding in the Mallard Anas platyrhynchos. Ornis Scandinavica 15: 261-265.here.
