Thursday, 14 October 2010

One, two, three...ten long-tailed tits

ResearchBlogging.orgThis time of year, the shrill 'see,see,see' contact calls of Long-tailed tit flocks, coming from all directions from the tree canopy. These fluffy, tiny birds have a fascinating breeding system - facultative co-operative breeding - by which individuals may help rear up offspring of others depending of the circumstances. Their breeding season is rather short, and they are only able to rear a single brood per season. In the spring, all individuals pair up and attempt breeding, if breeding fails early enough - mostly due to predation - , they attempt nesting again.
A predated nest of long-tailed tit on the 25th of April this year, the intact nest is a ball with the outside made of a delicately shell of pieces of lichen attached with spider webs, the inside is a down and feather filling. It can take the pair up to three weeks to put together.

In contrast, if a brood is lost late in the season, individuals may turn to help other nest owners raise their brood, bringing food for their offspring, and actually increasing the fledging rate. Who do long-tailed tits help? The theory of kin-selection predicts that individuals should help their relatives for cooperative breeding to persist. Do long-tailed tits do this? How good are they discriminating their kin? Is the amount of help correlated with the degree of kinship? Prof. Ben Hatchwell, from the University of Sheffield, has been studying a population of long-tailed tits for over 14 years, and his research has provided wonderfully detailed insights on the reproductive behaviour of the long-tailed tit. Apparently long-tailed tits are able to recognize their kin through their contact calls. In a new study by Prof. Hatchwell's group, kin relationships between most individuals in a valley near Sheffield (U.K.) were assessed using pedigrees and genetic markers. Then they followed the nesting attempts - on real, amazingly cryptic nests, not in nest boxes! - and estimated provisioning rates by the different carers. This way they were able to document the relationships between helpers and the individuals they helped.
The first interesting result, is that social ties are very good predictors of paternity in this species, there were no instances of cukoldry. Pairs were monogamous for each breeding season. This meant that pedrigree data was a very good predictor of genetic relationships.
  In many other cooperative breeders helpers often provision their siblings - that is, they are previous years offspring that delay they reproduction to help their parents raise another brood. In the case of the long-tailed tit, helping another nest is dependent on an own nesting failure, and there is a lot of diversity. Individuals can help their offspring, one or both parents, aunts and even a case of an individual helping a grandparent!. Most of the cases, however, involved individuals helping their siblings rear their nieces and nephews. This is possibly related to the high 'divorce' rates in long-tailed tits. Pairs are monogamous during a particular breeding season, but mortality is high (50% from one season to the next) and individuals often switch partners, therefore, the chances of a individual helping their parents is reduced. Also, siblings often disperse together to new territories so there is more opportunities to help a sibling than any other relative. In conclusion, most cases of help were to relatives, supporting kin-selection theory. However, things are often more complex than that: 23% of the helpers actually helped unrelated individuals. When the researchers looked at this in detail they saw that they were unrelated, but not unknown. Individuals helped other individuals with which they had social ties: previous year's partners - no hard feelings! or they helped in nests where another 'ex' was also helping. Maybe there is an element of reciprocity there. These results could make you think that long-tailed tits help guys they know, and the fact that they often help kin is just but the consequence that they tend to know their siblings socially, but it is more interesting than that.
Another, key prediction of kin selection theory: helpers should invest more the more related they are to the individuals they help (that is, helping is a cost and they should adjust the costs to the benefits). With their data of provisioning rates, they could indeed confirm that this is true: helpers provisioning rates increased with the relationship to the nestlings they fed.
Therefore long-tailed tits do recognise kin and preferentially assist them, providing support for the role of kin selection in the evolution of their breeding behaviour.
At the end of the breeding season, family groups come together in flocks, that will joining other tits and small birds and wander around the canopies throughout the winter.


More information
Nam, K., Simeoni, M., Sharp, S., & Hatchwell, B. (2010). Kinship affects investment by helpers in a cooperatively breeding bird Proceedings of the Royal Society B: Biological Sciences, 277 (1698), 3299-3306 DOI: 10.1098/rspb.2010.0737

Monday, 17 May 2010

Goldfinches and dandelions

You don't need to get out much to enjoy wildlife. Literally, sometimes surprising things happen right at your doorstep. This morning I had to stop short of opening my front door as I realised a pair of goldfinches were standing next to it. One of them was grabbing a couple of dandelion heads - that had probably tumbled over with its weight - and feeding on the unripe seeds. This went on for quite a while. The photographs were taken through glass.



Goldfinches are specialist on small seeds, they benefit greatly from flocking when foraging as they need a lot of effort to obtain enough biomass from tiny seeds that have to be prepared and swallowed one by one and they can devote less time to scanning for predators when they are in a flock.
Gluck investigated these effects on Goldfinches feeding in orchards in Germany during the breeding season. He recorded Goldfinches feeding on milky ripe seeds from 20 plant species. Of these, most of his obsercations were on five species: Dactylis glomerata (Gramineae), Knautia arvensis (Dipsacaeeae), Senecio vulgaris, Taraxacum officinale and Tragopogon
pratensis (Compositae). The following graph illustrates the relationship between the number of dandelion seeds ingested per minute and flock size in Goldfinches, showing that even in small flocks of 5 birds each bird can almost double their seed intake per minute.


I am a big fan of dandelions and today's sighting is going to make me do even less weeding around the garden.

More information
Erich Glück (1986) Flock size and habitat-dependent food and energy intake of foraging Goldfinches. Oecologia, 71:149-155. here.

Saturday, 1 May 2010

Worms, quick, quick!

Blackbird fledglings are out and about. Their urging 'quick, quick' calls to their parent to bring food make them easy to track. If the female is not ready to lay a second clutch, the pair of Blackbirds will divide the care of the brood amongst for up to ten days after the young leave the nest. If the female has already started laying, then the male takes care of the whole brood, running back and fro in search of food for his demanding young. This behaviour is a trade-off: the male taking charge allows shorter intervals between broods - and therefore higher chances that more chicks are produced in a season - but the more young he is feeding, the lower the chances they will all reach independence.
Yesterday, a male sang while it flew toward his charge, like he didn't want to waste a minute - a stressed, multitasking parent. Then, landing nearby, caught a large earthworm and banged it against the ground several times while the fledgling called insistently. The male offered the worm to the young, and he swallowed it voraciously.

Gradually the young will learn to catch prey or find food by themselves, and by 2-3 weeks after leaving the nest they will reach full independence.

More information:
PHILLIP J. EDWARDS (1985) Brood division and transition to independence in Blackbirds Turdus merula. Ibis, 127: 42-59. here.

Nest Calling Woodpigeons

Woodpigeon pairs are already formed and nest building is underway. For quite a while I have become accustomed to an unusual song of the Woodpigeon. It starts like it is going to deliver the usual five-syllable song, but instead it stalls and it only delivers two long notes, 'coo, coooo' with the second note dragging on - it reminds me or a revving motorbike. After a minute or so, the two notes are repeated, and it can go on like that for quite a while. I have heard it mostly when the pigeon is concealed from view (inside a cypress) and in one occasion I saw it delivered by a pigeon sitting on its nest. A pair of Woodpigeons have made a nest on a fork in a large weeping willow and the pigeon in the photo was calling in such a way. This call has been named 'the nest calling' and is uttered by the male showing the female a nesting site. According to Murton and Isaakson:

Nest calling is a submissive display, mainly shown by the male and is used to attract the female to the nest or potential nest site. Caressing can occur at the same time as nest calling or away from the nest, and possibly evolved from the food begging movements of the nestling. It usually precedes courtship feeding. On the physical level the display is used to stimulate ovulation in the female, so that when used for long periods in the absence of courtship feeding it appears as a ritualized display.


And according to Cramp:

From early January, and often soon after the pair is definitely formed, the male begins to mark suitable nest sites by Nest Calling. He crouches on the proposed site (which may be a bare fork or branch, or an old nest) and makes short, sharp, downward pecking motions, 
accompanied by the special nest call—a deep, double note, `coo, coo'.
The male may `nest-call' at several sites, and I imagine that the female normally makes the final choice, for the nest is by no means always built on the site where her mate has `nest-called' most persistently. The first nests are seen normally towards the end of March, and the majority start to sit in April.

More information:
Cramp, S.(1958) 'Territorial and other Behaviour of the Woodpigeon', Bird Study, 5: 55-66.here.
Murton, R.K., A. J. Isaacson (1962) The functional basis of some behaviour in the Woodpigeon Columba palumbus. Ibis: 104: 503-521. here.

Wednesday, 28 April 2010

Eight things I didn't know about swifts

The first Swifts are back! These extremely aerial birds spend just three months of each year with us, from early May to early August - their breeding season - but their continuous flight and noisy chases makes them obvious and fascinating birds to watch. They eat, sleep and mate and collect their nest materials on the wing. I recently read "Swifts on a Tower" by David Lack. A very informative and entertaining book, it is based on the observations of David and Elizabeth Lack and their students. They observed nesting swifts on modified nesting holes in the tower of the Oxford University Museum of Natural History, a building of fame due to being the place where the famous debate on evolution took place between Samuel Wilferforce and Thomas Henry Huxley seven months after the publication of the Origin of Species.
Museum of Natural History (Oxford) the central tower ventilation shafts (10 on each side) are the entrances to the Swift nests. Photo by Michael Reeve, licensed under Creative Commons, from Wikipedia.

Based on this book and more recent research I have compiled this list of facts that I didn't know about swifts.
  1. Their young can survive up to 21 days (!!!) with no food. Their growth patterns match the weather so that they stop growing during cold, wet or windy weather. The length of time they take to leave their nests depends as well on the weather, the earliest leave at 5 weeks, the latest at 8 weeks.
  2. Eggs can get cold (i.e. left by the adults without incubation) for at least two days and survive.
  3. Swifts - and possibly other bee-eating insects - can distinguish drones from bees and drones are the ones they eat, avoiding getting stung by workers.
  4. Swifts fight for their nests cavities by grasping each other's claws. The winner is the individual that can get on his back, so that it can push the other out of the nest.
  5. Adult healthy swifts can indeed take off from the ground. It is the recently fledged individuals in not so good condition that can't (they leave the nest early and their wings are not fully grown.
  6. Once fledged, young swifts are completely independent and receive no further parental care. They return to their summer grounds to breed when they are 3-4 years of age.
  7. The young join non-reproducing birds to sleep on the wing high up on the sky.
  8. Swifts are the fastest birds during self-powered flight (the peregrine "free-falls" using gravity to accelerate) reaching over 110 km/h in their 'screaming parties'. More info here.
More information:
For an informative article by the 'guardians of the tower' see here.


Henningsson, Per, Johansson, L. Christoffer, Hedenström, Anders (2010) How swift are swifts Apus apus? Journal of Avian Biology, 41: 94-98. Here.
Check the fantastic photos of swifts on flight by Jean-Francois Cornuet here.

Monday, 29 March 2010

Mate guarding in Mallards

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.

Monday, 22 March 2010

A gentle side of crows

The resident pair of crows were sitting on an aerial this morning, and the individual to the right was cawing. I was waiting for it to call again camera in hand - I like the arched necks and up and down powerful movements of crows cawing. Instead, after a few moments, the other individual approached its mate and began preening. Carrion Crows, as other corvids, form long-term typically life-long partnerships, where both pair members share most of the duties. In fact, the only noticeable division of labour is incubating and feeding the young nestlings. Pairs remain and defend their territory together year round. Usually, the pair defend the same territory year after year. Pair cooperation takes the form of aggressive territory defence from other crows but also other species which might compete for food. Both members of the pair approach intruders and engage in duet cawing, apparently inciting each other to attack them. They will also carry out 'pincer tactics' in which each member of the pair try and face each other keeping the intruder in the middle. Carrion crow intruders are the main nest predators, with up to 50% of their nests being robbed by other crows,  so it is important to keep them away from the territory.

More information
Bossema, I and R.F. Benus (1985) Territorial defence and intra-pair cooperation in the carrion crow (Corvus corone). Behav Ecol Sociobiol. 16:99-104. here.
Nicola S. Clayton, Nathan J. Emery, The social life of corvids, Current Biology, Volume 17, Issue 16, 21 August 2007, Pages R652-R656, ISSN 0960-9822, DOI: 10.1016/j.cub.2007.05.070.here.

Saturday, 20 March 2010

Uneasy neighbours: Carrion crows and Kestrels

A kestrel has taken residence in the neighbourhood, I have seen it flying almost every other day. The resident pair of crows does not seem happy about this. A couple of weeks ago I saw them mobbing the kestrel while regularly uttering their characteristic 'krrr' call high over the garden. The same happened yesterday. In both occasions, by the time I had taken the camera out they were already quite distant. As I wanted to write a post about mobbing, I decided to take out my Wacom Bamboo tablet and sketch the behaviour. Mobbing is found in many bird species and often is a communal affair by which potential prey call and harass a predator. Mobbing is a costly behaviour, it takes a lot energy to chase and call and dive bomb the predator. The crows can spot the kestrel in the distance and go out of its way to mob it. Once a kestrel was gliding quite high, and I watch a crow laboriously gaining hight in broad circles in order to mob it. During the actual mobbing, the crow flies slightly over the kestrel - a safe way to do it - and chases it, occasionally taking dives at it, while the kestrel avoids each dive, and occasionally turns to the crow. In rare occasions, the mobber can turn into a meal for the mobbed, but I am not sure this can happen in crows, which are quite robust and bigger than kestrels. Why do birds mob? what do they gain from this behaviour? There are many hypothesis and it is likely that a combination of some of them is the reason. One of them is that mobbing allows birds to transmit information on who the enemy is to the next generation (a form of cultural transmission). In some classic experiments with blackbirds, birds watching a harmless, novel bird being mobbed by another blackbird started to mob the new bird themselves. Mobbing can have also direct benefits for the mobbing individual, it could be showing off is good condition, a form of advertising that if wont be easy prey. Mobbing could confuse or distract a potential nest predator from their nest seeking behaviour. When the predator is chased and engaged it cannot pay attention to the local territory and gather information on the nest location, for example. In seagull colonies, mobbing on crows - yes, crows can be mobbers or mobbed themselves - decreased the chances of egg predation and colonially nesting gulls enjoy lower rates of nest predation than solitary nesting gulls. In addition, mobbing tends to intensify during the breeding season in solitary nesting birds.

This crow is gathering nest material, soft bark from the lime nearby. The photos were taken trough glass.
Crows are indeed nest building now. Yesterday and this morning we watched the pair gathering nest lining material, stripping pieces of lime bark dextrously using their feet and beaks. Their zealous harassing of the kestrel might well reflect the fact that they would rather not have him as neighbour when their vulnerable offspring hatches.

Tuesday, 9 March 2010

Nesting Rooks

Rooks are not common birds in the city, they suddenly appear when houses make way for the first grassy fields in the outskirts. Somewhat surprisingly there is a small rookery in the university grounds. Probably the large mature trees attract them. They are not present year round though. I heard a group in January and I hadn't heard them again until today. Suddenly, they have taken over the place having decided that it is nesting time. Their constant, excited drawn out single 'kaah' calls - quite different from the repeated, harder and sharper calls of the Carrion Crow - filled the air. There were at least five evident nests in construction - all of previous years nests all fell out with storms and high winds - , one just a little jumble of sticks. Rooks break off twigs and branches from trees instead of collecting nest materials from the ground, and they were coming and going from their nests to a nearby Alder where they broke off twigs for their nest. It has been suggested that collecting branches from living trees allow for better size and strength selection This description taken from Bayne, 1929 was very fitting today, with squabbles at some nests possibly as a neighbour tried to steal a precious stick.

"Most birds do their nest-building quietly and as secretly as possible. But the rooks cannot hide theirs, so they talk about them freely. Every time they come back with a twig they shout the news to the whole rookery and to any one else who may be able to understand them. But it is dangerous for them to boast too much about a stick, for it may be stolen by a neighbour when they are gone to fetch another." 

This series of photos taken on a few minutes illustrates the activity in the colony.
A Rook leaves its nest calling
This three Rooks were collecting sticks atop an Alder. The bird on the right has already got its stick.
This bird spend a good few minutes wandering aroung the tree undecided and left with nothing.
Bird returning with a branch
For this one a little twig will do




Friday, 5 March 2010

The surprising moorhen

Moorhens breed every year in my local park and, for moorhens, they are quite tame and allow close approximation. In the countryside moorhens are more difficult to see, their loud "kirr-up!" call, often giving away their presence while they feed in marginal vegetation of canals and rivers. Moorhens are unusual in several ways. First, contrary to most birds, females compete for males, engage in female-female fighting and initiate courtship. In most bird species, females carry most if not all of the burden of parental care, they make energy-rich eggs, do most or all of the incubation and in several groups they protect and or feed the chicks for some time after hatching. No surprise then that males compete for such good assets and female are quite choosy as to which males should father their offspring!
Incubating moorhen
In contrast, Moorhen males are devoted dads and carry out most of the incubation and tending of the chicks. Some males, those with good fat reserves are better at incubating than others. Small males then to accumulate more fat reserves, and females fight to pair with those small fat males. There are also male fights but they are for territorial defence, instead of fighting for access to females.
An adult searches for food while a young chick begs on the water edge
Both males and females tend the chicks, which are quite mobile from birth, but need feeding and are shown what to eat by their parents. The other unusual habit of Moorhens is that chicks from the first brood often stay around in their natal territory and help feed their siblings from the second (or third) brood. This cooperative breeding is also found in Swallows and Long-tailed tits in the UK. As territory availability is very constrained due to aggressive territory defence during the summer, young first-brood moorhens are forced to stay in the parental territory and cannot easily disperse. The more food resources are available in their natal territory, the more likely is that first brood chicks will help raise their siblings and the more effort they put into it. Helpers can make a difference in the number of surviving chicks for the second brood and also reduce the parent burden when feeding the second brood.
Courting pair just before mating. A young chick was in their nest nearby.
A tiny chick still in the nest with its parents
More mobile chicks follow one of their parents
These fledglings were chased up the tree by an adult
Pair of moorhens foraging on frozen pond
References
Eden, S.F. (1987) When do helpers help? Food availability and helping in the moorhen, Gallinula chloropus Behavioral Ecology and Sociobiology, 21: 191-195. Here.
Petrie M (1983) Female moorhens compete for small fat males. Science 220: 413-415.

Saturday, 27 February 2010

On Sparrow Bibs

Male sparrows are now beginning to show the urge of starting their breeding territories. I have seen several males chirping constantly from house eaves, a common nest site. When chirping, sparrows show off their fluffed up black chest bib. Sparrow bibs vary considerably in size between individual sparrows.


Figure showing variation in badge size in Male House Sparrows (from Moller 1987). See also the photos below.

Research has shown that bib size functions as a 'badge of status' and individuals with large badges enjoy a dominant status in the flock. Large badge individuals also obtain earlier mates as females prefer them and enjoy more reproductive success. Males with large badges seemed also better at defending their females from sexual harassment in multi-male chases. Large badges carried a cost though. Sparrowhawks, the main predators in the study took males with large bibs more often than males with small bibs during the autumn. The explanation was than high reproductive success had a cost in the condition of the bird at the end of the season. The study showed that sexual selection - female choice - and natural selection through predation acted in opposite directions in determining bib size.
A large bib male in my garden flock
A small bib male
References
Moller, A.P. 1987. Variation in badge size in male sparrows Passer domesticus: evidence for status signalling. Animal Behaviour, 35:1637-1644. here.

Moller, A.P. 1989. Natural and sexual selection on a plumage signal status and on morphology in house sparrows, Passer domesticus. Journal of evolutionary Biology, 2:125-140. here.

Thursday, 25 February 2010

On zebra mussels and tufted ducks

One of the most common diving ducks around here is the handsome Tufted Duck (Aythya fuligula). The male striking black and white plumage, long tuft of feathers at the back of their heads and yellow eyes makes them quite distinctive. Females are all brown and have only a tiny, but clear tuft. Reading about tufted ducks I came across some research suggesting that the spread of a non-native invasive species, the Zebra Mussel (Dreissena polymorpha) in the UK in the last couple of centuries could be linked to the increase in Tufted Duck numbers.
 Tufted ducks dive up to 5 m of depth to feed. They eat mostly zebra mussels where they are available, whereas in places where zebra mussels are not widespread, their diet is more varied, with crustaceans, insects, seeds and some molluscs. The mussels, which are of small size are swallowed whole and crushed in the muscular gizzard. The small mussels are sucked and filtered, while the larger ones require more manipulation.
and down it goes!
More information
Olney, P. J. S. (1963). The food and feeding habits of tufted duck Aythya fuligulaIbis105(1), 55-62. here.

Joep J. De Leeuw and Mennobart R. van Eeerden 1992. Size selection in diving tufted ducks Aythya fuligula explained by differential handling of small and large mussels Dreissena polymorpha. Ardea 80:353-362. here

Tuesday, 23 February 2010

Changing Heads

The first Black-headed gulls honouring their names have now appeared. The dark head is their summer attire and this makes them much easier to tell apart from the white headed, and very common, Common Gulls. This winter I have been testing my ID skills on flying city gulls. Black-Headed gulls are much more keen to pick scraps from the ground in busy streets and their flight is quite bouncy. The white front of their wing primaries can also be very obvious. I found the almost completely molted individual above in a local park on Valentine's day, and later, in a flock, only a couple of individuals have completed the molt, while most are on their winter plumage.

Saturday, 20 February 2010

Take a bow

There is a lot of Woodpigeon activity these days. I can hear the slow, five-syllable song continuously repeated from the aerials and trees in the street in the morning. The clapping of the territorial display, an exhibition flight, in which the Woodpigeon rises high noisily clapping its wings and then glides down in a circle with wings outstretched and kept horizontal. On a roof yesterday, a male and female were engaged in more active courtship. The pair makes these little jumps as they get closer to each other and they engaged in feeding, usually the male feeding the female.
This couple sat together for a while, but if courtship proceeds the male engages in a 'bowing display, with exaggerated, ritualised slow bowing until its beak touches the ground while lifting its tail and opening and closing it like a fan facing the female. The male calls at the same time. While singing the male ruffles his neck feathers showing off its side white and iridescent patches. If the female is ready she crouches opening its wings and the male quickly mounts her, otherwise, she will move away or try and peck the male or even fight him off with wing strokes.
 The following YouTube video shows a male courting a reluctant female.

Saturday, 13 February 2010

Greylag Geese watching

 In the last couple of weeks, a small flock of a dozen greylag geese has started to come to the local Park. Greylags are one of the most interesting local birds to watch. Once they land, the orderly formation breaks and pairs separate and noisily settle scores before starting their feeding with ritualized neck posturing. Despite being in a flock, pairs are usually quite easy to spot, they follow each other and the gander is slightly larger than the goose. When showing aggressiveness, one of the pair members lowers its neck and shows the beak to its opponent, with the partner following close. On quiet times, where no people are feeding the ducks, greylags head up to the large grass spaces of the park to feed. These are no wild geese, if you show some interest in them, they are likely to come closer to check if you have scraps, or even come right to you to demand some depending on their personalities. To watch them doing what if comes naturally to them you need to feign indifference. Today I watch six of them grazing.
Konrad Lorenz, the Nobel prize, carried out long term behavioural studies on hand-reared greylag geese to allow close approximation. His geese - which were individually named - lived free but did not migrate, so he could study them year round. Lorenz describes geese behaviour in detail in his book 'Here I am - where are you?' Lorenz first discovered the phenomenon of imprinting on geese, by which newborn birds attach themselves to the first moving object they see after hatching. The description of his first, serendipitous, realisation of imprinting is quite moving: 
'After the first gosling had hatched and dried, I was unable to resist the temptation of removing the delightful creature from under the foster mother and taking a closer look. As I did so, it gazed at me and soon began to utter its single syllable lost calls [...] I answered with a few comforting sounds. [...] Eventually, however, I had enough of this babysitting and placed the gosling back under the wings of the brooding domestic goose and started to leave. I should have known better.' 
The gosling started making distress calls and when Lorenz starts moving away, it follows him. Lorenz did a lot of babysitting from then on! 

The Greylag goose triumph ceremony (from one of Lorenz's papers on the behaviour of the Greylag geese).


Wednesday, 10 February 2010

The timid dove

You can consider yourself lucky if you have watched Stock Doves (Columba oenas) around. Compared with the obvious Woodpigeons and Collared Doves, and the tame ever present feral pigeons, Stock Doves are shy and unobstrusive. Their general dove-like appearance makes them almost invisible despite being relatively frequent in towns and villages. Although dull-grey from a distance, this dove is quite delicate at close range. It is shorter tailed and smaller than the Woodpigeon, being similar in size to the feral pigeon, but its dark wing bars are thinner and shorter and its eyes are dark, giving it a gentle expression. It has got an iridescent neck patch, shining green or violet, and an orange and pink beak. Unlike its relatives, it breeds on holes and therefore tends to occur linked to mature trees in parks and tree lined avenues with large gardens, although it also uses nest boxes (a couple used the owl box in the tree outside our house a few years back).
 Today, a rapid, persistent almost hiccupy cooing (uh, cu-uc! uh, cu-uc!) of a Stock Dove came from the large cypresses next to the park conservatory and a bird alighted on top of a nest box, giving me a rare photo opportunity.

A bill clattering crow

A few days ago I was walking past a wooded area in University when I heard a drumming noise. I though it was a woodpecker, and I stopped and watched. Not at all! A Carrion Crow sitting on a branch made this mute, bill clattering noise - in the most pure Stork style. The mobbing rattle is vocal, but similar in tempo. I managed to take a short video on it, must get round to upload it to YouTube and post it here. When clattering, the crow stood up and fanned its tail. It kept repeating the noise every few seconds. I could see no obvious context - no predators to be seen or even other crows.
More reading on Crow vocalisations here.