Saturday, 30 November 2013

Collared dove

Just a quick portrait post, with this collared dove portrait taken this summer in Pearson Park Wildlife Garden.

Thursday, 28 November 2013

Blackbird alarm calls

For a long time, I have been fascinated with the rich vocal repertoire of Blackbirds. I have recorded their alarm calls and what do they appear to react to, and did some research to find out what was known about them. Here I have compiled what I have found so far in my attempt to understand 'blackbirdese'. I have excluded male song and chick and fledgling begging calls from the post. Given how difficult is to transcribe bird sounds, I have illustrated each call with embedded sonograms and clips from the website Xeno-canto, which contains a fantastic collection of bird calls from around the world, published under Creative Commons licences.
Chink, chink, chink, chink, chink!'
A mobbing call given to owls, kestrel, magpie, carrion crow (and ornithologists checking nests!) which may be followed by attacks. The blackbird is exposed, agitated, flicks tail and wings - which are kept dangling -, from an obvious post (top shot and above) facing the potential predator, very nervous sounding and calling repeatedly and monotonously for a long time. It indicates a moderately aggressive tendency with a low escape tendency, although somewhat inhibited from attacking. Mobbing might be a way of cultural transmission of enemy recognition. Inexperience birds exposed to conspecifics mobbing a predator will join in the mobbing and mob the predator themselves in the future.

Alarm call before roosting or 'chinking'
Territory holding males give a persistent 'chink-chink' calls in the evening, possibly to deter other Blackbirds from roosting in its territory. Other territory holders might join in 'chinking'. This is interesting as it is very similar if not identical to the mobbing call. Is this a dishonest signal 'don't roost here, there are predators around'? or it is an assertion of territorial ownership with a general meaning 'move on'?

The bird sits tense, still, with feathers flat on the body and head. In response to crow and sparrowhawk, whether they are flying or just nearby. Slow, well spaced and high-pitched with open beak (above). Many other birds have a similar thin, high pitched alarm call for threats from aerial predators since the features of this sound makes the calling bird harder to locate, therefore the bird calling does not endangering itself. It has also been called 'hawk alarm', but it is also uttered in response to crows flying overhead or when the nest is threatened. Nestlings react to this call by becoming quiet and still. In experiments using magpie dummies, the parents uttered this call when the dummy was 6-7 m from the nest, while they used the mobbing call when the dummy was very close to the nest. Interestingly, there appear to be differences between urban and rural blackbirds use of this call, as D.W. Snow reported that woodland birds use this call also to humans (the one in the photo above is a woodland bird, so maybe was reacting to our presence), and then it indicates that the nest is very close.

Alarm rattle
A loud, sudden and accelerating outburst, ending on a noisy scream, with the bird flying away. Alarm call when the bird is suddenly startled, also during fights. May starts when the bird is perched but finished in flight. If this call has the same effect on a predator as if an observer disturbs a blackbird at close quarters - it has made me jump more than once - it might give the calling bird a few moments advantage to flee from danger.

Also called 'trill' call. A flight or fight intention call. Perched and in flight. It can serve as an appeasement call by a subordinate bird indicating its intention to flee.

Soft call
Also known as 'pok' or 'pook' call, sounds like a soft bark, to me more like 'wow'. Usually from a tree, still or in flight. It is an alarm call to indicate the presence of ground predators, which in gardens usually means the presence of a cat, or a human approaching young or the nest. Fledglings respond to this call immediately by keeping silent and still and looking around, and especially below them. D.W. Snow used a playback of this call to a few day old nestlings reared by him and they acted in the same way.

Low pitched, uttered with the beak closed. Anxiety call, mild alarm. Sometimes on its own, sometimes accelerating to the full-swing alarm call in flight. Flicks tail, horizontal body. To people, dogs, cats, etc.  Females use it when disturbed while looking for nest site or nest building. Also used when the bird is foraging in an unfamiliar situation where the bird feels insecure.

Chook, chook, chink, chink, chink
A variant in which the chook combines with chinking as the bird becomes more aggressive or excited.

More information

Snow, D. W. (1988). A study of blackbirds. British Museum, Natural History.

Kryštofková, M., Haas, M., & Exnerová, A. (2011). Nest defense in blackbirds Turdus merula: effect of predator distance and parental sex. Acta Ornithologica46(1), 55-63.

Tuesday, 26 November 2013

Having a very berry time

A few photos from my garden blackbirds taken yesterday, through two layers of glass. The rowan is still loaded with bright, fat berries, which seem to be keeping well. A female, above, about to swallow one. A male, below, had a quiet time after feeding.
This other male (below) has started visiting my garden recently. A quite distinctive individual due to the large white patches on his head. White feathers, often on the head, are quite common in my local blackbirds, but the extent of this individual white markings is the most extreme I've seen around here.

Monday, 25 November 2013

Urban Goosanders

A small group of Goosanders, Mergus merganser, are regular wintering birds in East Park. Not your typical urban bird, you might say, but they can be found in some parks with large lakes during winter, where they may occasionally come for bread (!) (see some great images here). They are stunning ducks indeed, males have black, glossy green heads, with thick, streaked plumage at the back of the head forming a 'bun', and white underside, with a tinge of pink/orange. The tinge in their plumage is caused by carotenoids pigments likely obtained from their diet. Females are grey, with creamy bellies and brown heads with a large fluffy crest at the back. The bill is long and thin, red with a dark hook. They are slim birds and float low on the water, and despite their long necks, they often keep them folded, giving the impression of having large heads.
 Yesterday, we visited the park and initially thought the birds were gone, possibly disturbed by some rowers training in the lake. Finally, we found a pair a the far end of the lake. The male was initially loafing in the shelter of low hanging willow branches near a male Pochard, but then joined the female and started foraging. Despite the urban habitat, they are shy birds, that take shelter near the islands in the lake, and tend to move away from people.
  Goosanders belong to a group called 'sawbills' due to the serrated edge of their bills that help them grip slippery prey, a good feature for a fishing duck. They eat fish, amphibians and aquatic invertebrates, including crustaceans, snails and worms. They rely on transparent water to fish, as they do it by sight, 'snorkelling' like grebes and cormorants do, with their forehead under water before diving propelling themselves only with their large webbed feet. They often probe with their bills on the bottom, to disturb hidden prey. They are also known to engage in communal fishing, where cordons of Goosander will corral fish towards the shallows and dive at unison to catch them.
 This species underwent an expansion during the last century from their Scandinavian range. They only started breeding in the UK at the end of the 19th century and in England since 1941. Now, they breed in upland rivers of Scotland, Wales and Northern England and winter more widely, with the wintering numbers boosted by birds also immigrating from the continent. In the early 1990's, coinciding with population growth in the UK, they started to winter in East Park, often in single figure numbers, with a maximum of about 30. Icy conditions might push them to last remaining open water in lakes, estuaries and sheltered sea shores, although they prefer freshwater.
  Goosanders - in a way similarly to other ducks - are unusual for birds, as males and females have different migration patterns. Most of the Western European drakes, including the British population, migrates to two fjords in northern Norway to moult their flight feathers between June and September, and then return to their wintering grounds in the UK. This male fidelity to their northern moulting grounds might be a cost of the expansion of the Goosander into southern Europe. Females, in contrast, moult later and more locally, late breeding females might moult on their local rivers before their offspring fledges, others congregate in local estuaries with an abundance of fish prey and presence of safe resting areas such as sandbars. It is not known how young birds find the moulting grounds, but association of young birds with more experienced ones in post-breeding roosting sites is a possibility. Pair formation takes place in the wintering grounds, from November-December, in their communal courtship.

The pair of goosanders with Black-headed gulls
Male Goosander 'snorkelling' and showing its 'bun'.
Female about to flap her wings, showing her creamy belly and shaggy 'hair style'.

More information
Hatton, P. L., & Marquiss, M. (2004). The origins of moulting Goosanders on the Eden Estuary. Ringing & Migration, 22, 70-74.

Little, B., & Furness, R. W. (1985). Long‐distance moult migration by British Goosanders Mergus merganser. Ringing & Migration, 6, 77-82.

Sunday, 17 November 2013

Charming seed predators

 ResearchBlogging.orgI find fascinating that when you seen something for the first time, then the chances are that you would see it again, seeing helps you see more. In the last couple of weeks a charm of goldfinches have been regular visitors in the garden feeders, gorging themselves on nyjer and sunflower seeds. I was watching the goldfinches and taking photos from inside of the house, when I noticed that one of the birds that couldn't get to the feeders was feeding on rowanberry seeds (above), discarding the pulp. This is typical of seed feeding birds like finches. Finches are seed predators, unlike thrushes, that eat the berries whole, passing the seed undigested and undamaged, in their droppings, and dispersing the seed away from the tree in the process.
 There was no mention of Goldfinches in the authoritative 'Birds and Berries' by Snow and Snow. I found a wonderful, if lone, photo on Flickr here and a line in a novel that suggested that this behaviour had been noticed before:
They went down the track through a wood where a flock of goldfinches was feeding on the rowanberries [...]
Tessa Hadley, Accidents in the home, 2002

Today on a walk in the park, I noticed a rowan on a garden and had a look. A charm of goldfinches looked busy on it. I wouldn't have normally had a closer look, but I did. They were feeding on the berries, hanging from the bunches like tits, not one, not two, but the whole flock seemed to be enjoying the berry seeds. The photos from today (below) are atrocious, as it was late and the light very poor, but a record nonetheless. After a while, something spooked the birds, a Sparrowhawk perhaps, and the Goldfinches went quiet and took to the air with a group of starlings and feral pigeons. I glimpsed what I think was a woodcock before if flew behind a roof, powerful wings and long bill, but just for a second. A Blackbird called: 'seee!' from a bush, their air predator alarm call.
 Indeed, a range of finches - including Goldfinches - are reported to feed on rowan seeds occasionally: Greenfinch, Crossbill, Brambling, Chaffinch, Hawfinch, Goldfinch, Redpoll and Siskin. Indeed, for some finches, particularly Bullfinch and Pine Grosbeak rowan seed in autumn can be their staple food. But rowan is a masting tree, where crop is very variable across years, with bumper crop, the 'masting years' interspeded with poor or failed crops in some. In the winter of 2004-2005, simultaneous irruptions of boreal Waxwing, Pine Grosbeak and northern Bullfinch occurred, all three birds liking rowan berries. Bullfinch local movements and irruptions in western and southern Europe have been linked to the strength of rowanberry fruiting crop.

This goldfinch appeared to use her foot to hold the berry in place

  A couple of weeks ago I spotted a juvenile Common Rosefinch, a rare visitor to these shores, feeding on rowan berries

Juvenile Common Rosefinch feeding on Rowan berries. 4/11/2013.

Some finches might use rowan depending on local availability. As this year rowan berries are plentiful and the thrushes have barely made a dent on the crop, Goldfinches and other birds may take advantage of this resource opportunistically.

Pennington, Mike G., and Eric R. Meek. (2006). The ‘Northern Bullfinch’ invasion of autumn 2004. British Birds 99: 2-24.

Munilla, I., and Guitián, J. (2012). Numerical response of Bullfinches Pyrrhula pyrrhula to winter seed abundance. Ornis Fennica, 89(3), 197-205.

Fox, A. D., Kobro, S., Lehikoinen, A., Lyngs, P., and Väisänen, R. A. (2009). Northern Bullfinch Pyrrhula p. pyrrhula irruptive behaviour linked to rowanberry Sorbus aucuparia abundance. Ornis Fennica, 86, 51-60.

Snow, B. K., and Snow, D. (2011). Birds and berries. A&C Black.

Raspe, O., Findlay, C., and Jacquemart, A. L. (2000). Sorbus aucuparia Journal of Ecology, 88 (5), 910-930 DOI: 0.1046/j.1365-2745.2000.00502.x

Wednesday, 13 November 2013

Watching Tufted ducks

Three Tufted ducks, either female or immature, have settled in the pond of my local park these last days. They have allowed me an unusual opportunity to watch them at close range - as the pond is quite small. They spend much of their time snoozing, preening, and diving. Although the light was a bit poor, the rich colours of the reflected trees on the water made up for it.
 They preen their bellies quite a bit, turning almost on their backs while floating in the water to do so. When they dive, they often do it together, diving one after the other. I had never seen a Tufted duck on land, but today, two of them spent a little time out of water, just by the pond edge, and then it became obvious how different their leg position and body shape is to dabbling ducks.

A good wing flapping after a grooming session

Showing its white belly while preening
Showing the heavy body and legs placed wide apart in the side of their body.

and an edited video of the Tufties

Three black birds turning leaves

The layer of fallen leaves under trees hides treasure for many birds this time of year: earthworms, woodlice, springtails, sprouting seedlings and more. I have filmed three bird species turning leaves in the park, each showing a different style: the Carrion Crow, slowly turning and tasting tidbits; the Blackbird energetically using its whole body, almost jumping, relying on an element of surprise, the moorhens looking like they are removing a nuisance from their way. Here you can watch the three clips.

Blackbird leaf turning

Moorhens leaf turning

Carrion Crow leaf turning

Monday, 11 November 2013

Gobbling up acorns

In the last few weeks it has become apparent that this is an acorns mast year, a bumper year for these seeds - and also for many berries. The evergreen oaks in my local park have not been an exception: Grey Squirrels and Woodpigeons are enjoying this bonanza and feeding on fallen acorns on the ground and the remaining ones in the tree. Today a large flock of Woodpigeons, including many juveniles, feasted on acorns in the park. I managed to record some videos of the feeding activities of the Woodpigeons in the trees and the ground underneath. I find it amazing that the Woodpigeons swallow the acorns whole, presumably their digestive system dissolving the tough shells.
At some point in the sequence, something scared the woodpigeons and most of the flock took to the air. The one I was filming stayed put in the tree, looking up nervously.

Friday, 8 November 2013

Birds and sycamore aphids

Sycamore aphids, Drepanosiphum platanoidis, are Sycamore specialists - and cover your car with honeydew if you happen to park underneath. All adults are winged and sit evenly spaced under leaves. In the spring, sycamores come alive with the calls of hungry Blue Tit fledglings demanding food. It is an easy job for the adults to pick the aphids from under the leaves to feed the chicks (above). Although many leaves have fallen now, there are still some in the sycamores, peppered with the black spots of, Rhytisma acerinum, the tar spot fungus, and some aphids are still in them. In the last few weeks I have seen Great Tits and Chaffinches feeding on them. Today, I watched a chaffinch hovering under the leaves picking the aphids, a most beautiful sight, which unfortunately couldn't catch on my camera.

Thursday, 7 November 2013

Autumn songs

Despite the days becoming shorter and darker, a few birds are still singing. Robins, both males and females claim their winter territories with their heartfelt, melancholic song, Wrens can be prompted to go on their outburst of song all year round, often by other bird calls and Starlings, donning their brightly spotty winter plumage call enthusiastically from chimneys and aerials.

Wednesday, 6 November 2013

Woodpigeons showing off

Woodpigeons come regularly to my bird table. These two arrived within a couple of minutes. I am not sure if they were a pair, but I doubt it, as they were not happy to be feeding so close. They alternated between feeding peacefully, and facing each other standing high on their tiptoes, chests up, measuring each other up. A bit of wing flapping occasionally - that is how woodpigeons fight, slapping each other with their powerful wings - but mostly just posturing. The photo was capture with my remote control camera.