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.

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.

Mistle thrush collecting nesting material

The resident pair of mistle thrushes rattled while flying to the lawns in the park. One of them fed on worms for a while taking little notice of me, but then it found a feather and seemed to have a change of heart, as it started to collect nest lining material enthusiastically, and then it flew to a large horse chestnut rapidly growing its leaves.

Carrion Crow begging to its partner

A Carrion Crow collected food in its bill and gular pouch on the University playing fields. Sitting in the nest atop a still bare ash, its mate called repeatedly, a begging, hoarse, nasal call, kaaaa! similar to a Rook's. The crow collecting food - most likely the male - looked up to the nest and flew heavily upwards in circles, stopping on a roof on the way. The female called again and flew off the nest to meet him, calling like a fledgling would do, crouching and wing flapping. The begging and feeding carried on out of sight on the roof.
In Carrion Crows, the female incubates and is fed by the male during this time, so it is likely that the nest on the ash tree already has eggs.

male crow collecting food for its mate

The female returns to sit on the nest (maybe already has eggs?)

The female's tail sticks up from the nest.

Woodpigeon nest calling

This Woodpigeon was nest calling 'coo, crrroooo!' from a fork in a still bare ash tree atop a nest (possibly an old one). Male Woodpigeons sign like this to their mates pointing to a suitable nest site and apparently also stimulating ovulation. Read more about this calling behaviour in this post from The Rattling Crow archives.

The scary bright eyes of the Jackdaw

Jackdaws breed in loose colonies, and unusually for corvids, in cavities in trees, cliffs or buildings. There is often very strong competition for nest sites, and the pair will defend their nest fiercely against conspecifics. Jackdaws are also unusual for having very contrasting, almost white irides. In a recent paper, Gabrielle Davidson and her colleagues from Cambridge and Exeter Universities tested the hypothesis that the bright, contrasting eyes of the Jackdaw serve as a strong warning signal when adults are occupying a nest, warning intruders not to come in.
 They set up 80 identical nest boxes in woodland areas in Madingley (Cambridgeshire) during the pre-breeding season (February-April), when Jackdaws prospect potential breeding sites. The nest boxes had two perches, one at the base and the other just by the entrance. They fitted the inside of the entrances of the nest boxes with a circular printout, visible from the outside. Each nest box was randomly assigned one of four types of printout: a dark circle (control) a dark circle with white 'eyes'  of the same dimensions of a Jackdaw (eyes only), a printout of a face-on photo of a Jackdaw with eyes retouched to increase the brightness (bright eyes), and the same printout but with dark eyes (dark eyes). They used remote video cameras to record Jackdaw visits to the nests, and the time they spent sitting on the nest itself and the perches.
 The results were striking. Jackdaws alighted on the nest box significantly less when the bright eye print was in the nest entrance. In addition, they spent very little proportion of their visit time on the perch closest to the entrance both in the eye only and bright eye treatments. The visiting Jackdaws actually entered the nest box in two occasions, one in the control and another one in the dark eye treatment.

This experiment shows that eye colour can be important in communication with conspeficics. The pale eyes are a warning signal to prospecting Jackdaws that a nest is occupied, and they avoid approaching the nest entrance once they are on the nest box. This reaction to an occupied nest reduces intraspecific conflict, as it might save them from a fight and potential injury. Davidson et al speculate that the 'eye fear' response of Jackdaws might be more general, and they might react in the same way to sparrowhawk eyes, for example, as it is known that they are sensitive even to eye gaze in humans - they will delay their approach to food if a human is looking at them.

More information
Davidson GL, Clayton NS, & Thornton A (2014). Salient eyes deter conspecific nest intruders in wild jackdaws (Corvus monedula). Biology letters, 10 (2) PMID: 24501271

Jackdaws inspecting potential nest site

A bright blue sky greeted us today. Days are getting longer and there is a certain spring feeling in the air. Jackdaws are not common birds in my local area, but there are a few, loyal to their territories, and usually nesting inside chimney pots. Today, I spotted a pair sunbathing on a tree, next to each other. After a while, they flew to a chimney and one of them - likely the male - inspected each of the chimney pots carefully, while the female sat around. Then he called and fluffed up its plumage and both flew to the other side of the street, meeting another pair. A Carrion Crow then landed on a aerial close to the chimney, came down and checked inside the chimney pots the Jackdaws had been inspecting. It looks like crows watch carefully what other animals are doing and like to check just in case there might be something in for them. In the case of nesting Jackdaws, the adults will rarely leave the nest unattended once there are eggs or chicks in it, as predation is the main cause of nesting failure.
 It is early for Jackdaws to start nest building, but their instincts are definitely stirring.

Hole number one, check

Hole number two, check

Hole number three, check

The individual on the left (prob the male), makes some soft calls with plumage fluffed up

The curious Carrion Crow watching the Jackdaws

More information
Coombs, F. (1978). The Crows: a study of the Corvids of Europe 255 p. London: Batsford.

School Martins

I always keep an eye for House Martin's nests near home. So far I had only counted three lone nests under house eaves, with evidence that before there were more together. Despite this lack of local nests, I see plenty of House Martins around in summer, and I often wondered where they nested. Last week I took a different route to work, hoping to see the last chasing swifts of the season. As I walked, I noticed the soft chirping of many House Martins, they were flying, circling just over a street and coming close and away a building. I approached them, a group of more than 30, probably including many juveniles. Some juveniles were still inside nests, and the coming and going of feeding adults was well underway. Their nests were located in a hundred year old building, a local primary school. The roof has wide eaves with paired beams, and many of the nests were placed in between the beams. I counted 18 nests on the east south side, some looking very fresh, and there were as probably as many more on the other sides. Lovely to see the activity of the colony, and also how vocal House Martins are when young are around, some chirping with a more shrill high call.
 I know now that these house martins spend the summer at school.

Nest tucked between the beams

Some of the nest on the building

Nest building woodpigeons

On a walk in my local park, I came across two different Woodpigeons collecting nest material. This is likely to be the second brood of the season. I stopped to try and get some shots of the second one. The nest was in a large Horse Chestnut. The Woodpigeon would come to the ground, walk to the pile of sticks that had fallen from the nest, peck them until one suited him, and then fly up to the tree. Occasionally, the stick would come tumbling down a few seconds later. I wonder if they were in the early stages of nest building and the platform wasn't stable enough. Usually one of the individuals of the pair bring the nest material to the other, which is sitting on the nest, and this individual arranges the sticks.
 I had a long session while sitting at the base of the horse chestnut. Every couple of minutes or so, I would have a chance to take a shot or two of the woodpigeon choosing a stick or flying up. The woodpigeon continued its merry-go-round taking no notice of me.

Breaking sticks

The nesting instinct is starting to stir in the Crows. Early last month, the pair above examined a nest from last year, one individual getting into the nest and doing some rearrangements. I am not aware of Carrion Crows reusing old nests, so maybe they were just suddenly experiencing an urge to sit on a nest again. I haven't seen the birds visiting the old nest again.
 Today, I noticed a crow struggling on a tree. It was trying to break a twig using all its might, flapping its wings and leaning back. Unlike other birds, which collect sticks found on the ground, Carrion Crows, Rooks and Jays use fresh sticks, that the break from trees as the material for the main framework of their nests. Then they will look for bark, hair and grass as lining lining on the ground. After a couple of unsuccessful attempts, the crow moved to another part of the tree, and this time it was successful first try, cleanly snapping the stick. It then rearranged the position of the stick to pick it up securely balanced from the middle, and flew away. The crow nesting season has already started.

Frisky Pigeons

All of January, Collared Doves have been playing their the three note song in a repetitive, mesmerizing soundtrack. Outside, display flights, in which the doves fly across the street of over roofs with wings held low as they descend, indicate that Collared Doves are starting to gear up for the breeding season.

Woodpigeons too. In fact, they seem to not have stopped breeding. In early November, I watched a fledgling begging for food in the park (above), and yesterday, I saw an immature with no signs of white feathers, feeding on the grass (below). The individual on the top shot appears to be a young pigeon growing its neck and head feathers.

Today, in the lime tree just outside my house a male Woodpigeon nest-called persistently while the female checked a pile of loose sticks on the first fork of the tree.

Even the Stock Doves, a normally quite discreet bird, also showed a lot of exuberant activity in the park. High flights, chases, courting and persistent song. A male tried to approach a female on a brach and she flew off (below).

The - so far - mild winter might be fooling them into an early breeding season.

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

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.

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