The Herring Gull pair at The Rock

More often than not there will be a Herring Gull pair by the pond in my local park. I assume it must be the same pair, as seagulls are long-lived birds and they behave in an aggressive way to immature gulls that land near the pond. This pair likes a particular spot which I call "The Rock", a vantage point on a promontory on the edge of the pond, and both individuals often stand there side by side.
 Today, a gang of excited Mallard males were giving chase to a female and one of them started mating with her. This behaviour is common in Mallards and is known as forced copulation, where there is no display and the female is corralled by males who are not their partners and forced to mate. The gull, which was very close, saw this, walked to the mating pair, and pecked the male! Not just a gentle peck, no, she even got some feathers out of him. This was a bit too much for the drake, his passion was quickly dispelled, he dismounted the female immediately and walked away a bit ruffled while the other drakes watched. Everything happened fast and I only had time to take a shot of the last part of the scene (below).

 Ouch!

The pair of Herring Gulls at the Rock 

Some twenty minutes later I noticed the pair were calling noisily with their miaowing calls, they were feeding on something on the ground. An egg! By the look of it it was a duck's egg all cracked and its contents spilled on the path. When I went to check, it had all the looks of an infertile egg. Still, the seagulls took turns feeding on it.

 One of the Herring Gulls feeding on the egg

The spilled egg

The bird with the silvery eyes

In his most amusing book King Solomon's Ring, Konrad Lorenz described his experiences rearing a veritable menagerie of different animals including jewel cichlids, water shrews, a raven, cockatoos geese and ducks. His intention was to develop an intimate relationship with them and understand their behaviour and communication. He reared the birds himself then set them free. This allowed him to have very tame animals that could be observed from close quarters. The longest chapter is devoted to his colony of Jackdaws (Coloeus monedula), which he started by hand-rearing more than a dozen of them. He ringed his Jackdaws with colour and metallic rings and named them accordingly to their ring colours. This chapter is a vivid account of Jackdaw behaviour. Lorenz was of the opinion that you had to get under the animal's skin to understand their actions, and his fascinating account shows that he got very close to feeling like a Jackdaw and he was definitely treated by one with a male that adopted him as his partner and insisted in feeding him chewed worms.

Flying together
Jackdaws are very sociable corvids, they like to fly in tight flocks. The members flock feed together and breed together in loose colonies in natural holes in cliffs and old trees and in buildings commonly using chimney pots. He described the "kia" call as equivalent to "fly away with me" and a longer version he learned to distinguish "kiaw" as "fly back home with me". His first jackdaw, Jock found dark birds flying away from him irresistible, and would often pursue a Hooded Crow away in his walks with Lorenz. Adults use this instinct to entice young to fly with them and will keep a close eye "looking over their shoulders" as they do so, to make sure the young can follow. Lorenz noticed how adults adjusted their flight and made it slower when fledglings were flying with them, making it easier for the young to follow.

The rattling reaction
One of the most surprising discoveries made by Lorenz was the instinctive basis of the rattling reaction and how . He found by chance - by taking his black swimming trunks from his pocket - that a dark floppy object held by something was a very strong signal that started a furious attack. His tame jackdaw attacked his hand drawing blood. The pecking was accompanied by loud rattling calls. In other occasions - such as when he intended to ring the young jackdaws in his colony, he observed that holding the feathered young will draws the members of the flock together into a rattling reaction. This presumably has the function that a predator that catches a jackdaw receives such a severe punishment. The memory of the offender is imprinted into all the members of the flock participating in the rattling reaction and will persist for years and form the basis of local traditions that will be passed down generations. As the rattling reaction was elicited when Lorenz held feathered young for ringing, he decided to dress up with the only outfit he had at hand - a devil costume -  and climb onto his roof to ring the young jackdaws. A sight that shocked some of the people of his village one day.

A pecking order
The jackdaw flock has a precise stable hierarchy. There is a pecking order in which "very high caste jackdaws are most condescending to those of lowest degree and consider them merely as the dust between their feet" according to Lorenz. Males, which are larger than females are higher in the rank. High ranking jackdaws always takes the weaker side when intervening on disputes, which helps maintaining the cohesiveness of the colony. The way Jackdaws assert their dominance is by raising the neck pale feathers.

A pair of jackdaws basking in the early morning sun

Lifelong partners
Jackdaws are socially monogamous and pair for life. Pairs form on the individuals' first spring, although they are unlikely to breed until their second spring due to a shortage of nesting sites. The partners in a jackdaw pair are together all year round and support each other loyaly in any dispute. The rank of a new female partner automatically rises correspondingly in the female's rank order, a refinement of Lorenz discoveries explained in the later monograph on Jackdaws by A Roell. Lorenz said he was surprised how quickly all jackdaws in the colony knew of the rise in rank of the new partner of the recently arrived alpha male. But not only that, the female also knew that now she stood over everybody else! The male will show the female a nest site by calling her with "zink" calls. The bond between the pair is shown by allopreening, usually by the female which will preen her partner's neck, particularly his silvery feathers. The female also will beg for food and the male will courtship feed her as he will in time feed the young. Both male and female share the building and defence of the nest and the rearing of the young but only the female incubates. During incubation, the male will feed the female.

The few pairs of local Jackdaws now sitting on their nests remind me of Lorenz entertaining book.

More information
Konrad Lorenz (1954). King Solomon's ring: new light on animal ways Methuen, London Other: 0415267471

Röell, A. (1978). Social Behaviour of the Jackdaw, Corvus monedula, in Relation To Its Niche Behaviour, 64 (1), 1-122 DOI: 10.1163/156853978X00459

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

Bold as a coot

Coots are the odd ones out in their family. Unlike other rails, they are bold, noisy and aggressive birds. Instead of searching for cover, they are all out, even their nests are usually placed in the open water and they are as prominent that you cannot miss them. Their squabbles amongst themselves and with other birds may carry out through the winter, as some birds keep their territorial behaviour year round. Coots have ashy-black bodies and black heads where a strikingly contrasting white frontal shield and beak is one of their most distinctive features. Unlike the long, thin toes of the Moorhen, coots have lobulated toes with side extensions - similar to a Grebe's - that allow them to dive in search of the algae and underwater plants that form a good portion of their diet.

The Coot "flippers"

But lets go back to the frontal shield. The size of the shield changes through the year depending on the bird reproductive status. Both males and females have frontal shields although the males' are larger, but both change in parallel, getting bigger in size as the start of the reproductive season approaches, and peaking in February -March.

(from Visser 1988)

Birds holding a territory have thicker and larger shields than birds not defending one.  Experiments on the American Coot, a close relative of the Eurasian Coot, showed that frontal shields enlarged when coots were injected with testosterone pellets, while they become smaller when injected with estradiol. At the same time, the birds climbed up in the pecking order when injected with testosterone due to an increasingly "pugnacious attitude" in the words of Gordon Gullion. The size of the frontal shield in European coots is also correlated with gonadal size. The frontal shield is apparently used for individual recognition and it is an important in territorial disputes or fights. When an intruder enters a territory, the resident bird will lower its head, raise its wings and prominently displaying their shield to the intruder. Like so...

A typical posture of an aggressive coot

I have much more on stock on Coots, but this will have to do for today.

More information
Visser, J. (1988). Seasonal changes in shield size in the Coot Ardea, 76, 56-63

Gordon W. Gullion (1951). The Frontal Shield of the American Coot The Wilson Bulletin, 63, 157-166

Snowy birds

It has been cold and snowy in the last few days. Berries that a couple of weeks ago were plentiful - are now in short supply, as the Blackbirds, Woodpigeons and thrushes have dug in. Flocks of thrushes are moving south to avoid the cold temperatures and entering parks and gardens. Birds used to feed on the ground have the added disadvantage of having their food under a layer of snow, and the ground hard and frosty. Blackbirds and Carrion Crows will persist if the snow is not too thick. They push the snow aside with their beaks to uncover their hidden morsels. The robin on the photo above looked a bit perplexed though.

Carrion crows searching on the snowy grass

This blackbird has dug himself a hole

The fascinating love life of the Dunnock

I watched a Dunnock today, feeding under the garden table, with that characteristic half hopping half walking way Dunnocks have, pecking here and there things too small to be seen at a distance, maybe seeds or small invertebrates. Dunnocks, or Hedge Sparrows (Prunella modularis) are little birds, which live their lives mostly unnoticed amongst the undergrowth and are easily overlooked or taken for House Sparrows. They have a grey chest and head and chestnut backs with dark stripes, a thin beak and orange legs. Both males and females look similar, females just a bit smaller than males. In gardens they often feed on the ground, under bird tables when there is some cover, and they prefer to skulk than to sit out in the open. Only in the spring, where males sing their weak, warbling song from a prominent perch they are somewhat more likely to be noticed (above). Contrasting with their modest attire and retiring habits the Dunnock shows a variable mating system - including a common arrangement of two males and a female, a system called polyandry- , and a courtship behaviour that can only be described as peculiar. I was lucky enough to witness courting Dunnocks a few years back. This is a sketch of what I saw and my description.

Female appears paler, less extensive grey markings than the male. Both individuals are on the ground. The male hops behind the female and she stops a moment with her tail slightly cocked and vibrating her wings, that are dropped.  The male pecks her cloaca repeatedly. Female hops away a little, male follows and the same behaviour starts again. Then the intensity increases, the male pecks her cloaca again and the female stops, then the male jumps on the female and there is a flutter

 What could be the purpose of this bizarre cloaca pecking behaviour? Has it got anything to do with the presence of polyandry? Nick Davies, in a classic paper published almost 30 years ago, provided some answers. He followed a Dunnock population in Cambridge Botanical Gardens. Males outnumbered females due to higher female mortality during winter, and therefore, there was intense male-male competition. He observed several combinations of breeding partners per territory, including male-female pairs, two males and a female (what he called trios), and some more rare cases including two males defending jointly the territories of several females.
Monogamous males guarded the female, following her around closely for a few days before she was due to lay and gaining almost exclusive copulations with her. When there are more than one male in a territory the larger male was dominant to the smaller one and fights were common, with the dominant male trying to chase the subordinate away from the female. Although the dominant male got the best share of copulations, the subordinate also got them as he was usually very persistent and mated with the female unnoticed by the dominant male, or when the male lost track of her - often after a fight. In all events of courtship, be monogamous males or not, the female always exposed her cloaca, often a pumping action was noticed and the male pecked it. After cloaca pecking, the female was seen to eject a droplet of fluid. Davies managed to collect three of these droplets and when he examined them under the microscope he found them to contain bundles of sperm. When he watched the female ejecting the drop of sperm, the male copulated with her immediately after. The purpose of the cloaca pecking behaviour appeared clearer: the male stimulates the female to eject stored sperm from the previous mating, allowing the suitor a shot at paternity. This was confirmed by the fact that the more other male spent near his female, the more a male pecked the female and copulated with her, as the male pursued to increase their chances of paternity. Interestingly, the female played an active role in being part of a trio:  she tries to obtain copulations from the subordinate male, escaping the guarding of the dominant, despite his efforts: obviously ejecting sperm from the previous mating will offer both males a share of paternity. When a female was observed to have mated with two males, the brood raised was fed by both males. In contrast, if the subordinate male failed to mate with the female, he did not contribute subsequently to raise the chicks. As nestlings fed by two males have a better chance of survival, it appears that is in the female interest to mate with both males.

A subsequent study using DNA fingerprinting confirmed what behavioural observations had strongly hinted: monogamous males got 100% paternity, and both dominant and subordinate males fathered chicks (surprisingly more or less equally). The observant reader will notice that the mean paternity of dominant and subordinate do not add to 100% in the polyandry system. This was because an outsider gained access to the female and fathered a chick.

(modified from Table 1 from Burke et al 1989).

Furthermore, this study showed that the chances of males helping the female rear the brood were dependent on them having sired some of the brood. It appears that the male is able to judge if he has had sufficient access to female to gain some paternity and to be worth the effort of helping her rear the chicks.

Although cloaca pecking can be seen as the male bird trying to ensure his paternity, the elaborate courtship of the dunnock also reflects that females are active participants and, that, as they need more than a single male to rear her chicks, this unusual courtship is the way females ensures that both males help her raise her chicks and that she achieves more reproductive success.

A pair of Dunnocks in the garden. What would they be up to?

More information
Davies, N. (1983). Polyandry, cloaca-pecking and sperm competition in dunnocks Nature, 302 (5906), 334-336 DOI: 10.1038/302334a0

Burke, T., Davies, N., Bruford, M., & Hatchwell, B. (1989). Parental care and mating behaviour of polyandrous dunnocks Prunella modularis related to paternity by DNA fingerprinting Nature, 338 (6212), 249-251 DOI: 10.1038/338249a0

Opportunistic crows

 Corvids are omnivorous birds and display a very flexible and opportunistic feeding behaviour: they will exploit coastal resources when near beaches, will actively search for nests in the spring looking for eggs or chicks, will take advantage of human scraps, feed on roadkill or other carrion, or look for worms and other invertebrates on fields and woodland floor. They show a remarkable inventiveness regarding looking for food, leading in some species to an understanding of the manufacture and use of tools. Rooks are able to add stones to a beaker with a little water where food is floating until the water level rises enough for them to reach the food. Caledonian Crows craft tools - including hooks - from leaves and twigs and use then to fish out grubs from trunks. Other species, like Jays, have extraordinarily precise spatial memory, which allows them to cache food surplus for use later.
  In general, corvids are dexterous birds. They have excellent foot-beak coordination and often use their feet when feeding, to hold down a piece of food so that they can pick bits with their beaks, as the Carrion Crow above. In experimental set ups, Ravens are able to reach meat tied to a a long string by alternatively pulling with their beaks and stepping on the loops of the string with their foot.
Their catholic food preferences and ingenuity have undoubtedly allowed them to adapt to living near people, and some crows species, like the Carrion Crow are common in towns, cities and agricultural land.

 Carrion Crows and a Greater Black-Backed gull feeding on a dead seal pup and afterbirths on a Grey Seal colony

I saw this Carrion Crow flying with a Woodpigeon's egg on its beak. It landed and quickly opened it up and ate the contents 

The predated egg shell

Carrion crow searching for a nest while a blackbird gave alarm calls nearby

Crow feeding on a chick 

Rooks and Carrion Crow feeding on a beach

A short video of a pair of Carrion Crows feeding on the leaf litter

More information
Bird, C., & Emery, N. (2009). Rooks Use Stones to Raise the Water Level to Reach a Floating Worm Current Biology, 19 (16), 1410-1414 DOI: 10.1016/j.cub.2009.07.033

Hunt, G., & Gray, R. (2004). The crafting of hook tools by wild New Caledonian crows Proceedings of the Royal Society B: Biological Sciences, 271 (Suppl_3) DOI: 10.1098/rsbl.2003.0085

Heinrich, B., & Bugnyar, T. (2005). Testing Problem Solving in Ravens: String-Pulling to Reach Food Ethology, 111 (10), 962-976 DOI: 10.1111/j.1439-0310.2005.01133.x