Monday, 5 March 2012

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 seagull, 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

Saturday, 3 March 2012

The bird with the silvery eyes

ResearchBlogging.orgIn 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