Thursday, 17 November 2016

Playing herring gulls

This morning at a local park, I noticed a young Herring Gull picking an object, flying off and being chased by another. Then the gull landed on the water and dropped the object and pretended to dive to pick it up repeatedly, as in a lazy drop-catch game. When I saw the object at a better angle I realised it was an empty freshwater mussel shell, which happened to float. Funnily enough, a couple of hours later when I walked past either another or the same young Herring Gull was still playing with it.

The young gull flies off with the freshwater mussel shell.

Later on, with cloudy weather, two gulls handling the shell.

Wednesday, 16 November 2016

The bristle head crows

Carrion Crows have a complex social structure. Territory-owning Carrion Crows remain paired year round, often flying and feeding together or not far from one another. They remain near their nest during the breeding season, although they may range wider outside this period. Birds that don't hold a territory form part of a loose flock that roosts communally, usually in large trees. Both male and female of a pair participate in territory defence, keeping other crows (or potential predators) away from the nest. Males have a more prominent role: if a male loses his mate he is able to defend the territory until he remates, but a female losing his mate will also lose her territory, as she would rapidly be evicted by other pair.
In one of my local parks there is a very high density of Crows. There are several territories, but the park is also the main ranging area of the non-breeding flock (where there is also a winter roost). There are a lot of interactions going on, but without ringed birds, it is hard to make sense of what is actually happening. Yesterday, I observed several interesting interactions. First, a Black-headed gull appeared most annoyed with a Carrion Crow and mobbed it repeatedly, dive-bombing on it when the crow tried to stop on an aerial. The crow did not vocalise and deftly avoided the gull attacks. Later, I heard the rattling call of a crow and watched a chase between two crows, one of them calling with the call I usually associate to mobbing a raptor. Crows, it appears, can use this vocalisation to fend off conspecifics.
 Finally, I watched a Crow it an amazing display: its head feathers raised, bill pointing down, looking really at its best. After taking a few photos, I realised it's partner was walking nearby using the same posture. Today I learned about this display in 'The Crows' by Franklin Coombs. It is called the 'Bristle head' display. It is a territory-owner display, used in territory boundaries to signal their occupancy, and also aimed at intruders within the territory. Both members of the pair display while they walk about. There is no vocalisation. Territory intrusions mostly occur during the spring, but there is also a peak in October-November.
 I can only presume that this pair of crows are a pair ot territory owning breeders. They do look in great shape!
This is a still from a video, which shows both members of the pair with their 'bristle heads'.
A side view of the displaying crow. 
This photo is a bit overexposed, but it shows the details and metallic iridescence of the crow really well.

Wednesday, 9 November 2016

Chok, chock, chock!

I've been wanting to take a photo of a Blackbird in this posture for a long time. Blackbirds do often cock their tails. When they alight they do that tail-cocking so as to keep their balance - in a similar way to Woodpigeons - they often do a jerky tail-cocking action when they do one of their various alarm calls 'chok, chok, chok' at the same time than they flap their wings. On Sunday, a windy day, this Blackbird perched on the side of a drinking trough, the wind made it lose its balance a bit and it stayed, tail cocked, for that second longer for me to press the shutter. Got you!

Saturday, 1 October 2016

Great tits feeding on horse-chestnut leaf miner

In a walk around the local park, a pair of Great Tits called my attention. They were calling and foraging in a horse chestnut. I watched how dexterously they grabbed the large leaves with their bills, pulled them towards them, and held them with one foot while feeding (top shot). They were looking for larvae or pupae of the horse chestnut leaf miner, Cameraria ohridella, a micromoth that has expanded its range throughout Europe from its native Balkans. The moth's larvae feed inside the leaves of the horse chestnut, leaving them speckled. Blue tits also feed on this leaf-miner (as do Marsh Tits), and I've seen them feeding on them before, but as they are lighter than Great Tits, they are able to just hang from the leaves themselves.
This is a short clip documenting this behaviour.

More information
Grabenweger, G., Kehrli, P., Schlick‐Steiner, B., Steiner, F., Stolz, M., & Bacher, S. (2005). Predator complex of the horse chestnut leafminer Cameraria ohridella: identification and impact assessment. Journal of Applied Entomology, 129(7), 353-362.

Friday, 26 August 2016

Beach pigeons

In my recent holidays, it wasn't only the local Carrion Crows that visited the beach at low tide, Woodpigeons and Collared Doves regularly popped in. The first day I noticed a Collared dove on the sea defences pecking on something, when I looked closer I realised it was eating seaweed (Fucus spiralis, I believe), something I hadn't seen a bird do before.
Collared Dove enjoying some seaweed on the sea defences, as they do.
I took a video the following day.

In subsequent days I watched the visiting woodpigeons, which were keen beachcombers...

...but when a female landed on the beach, a male keenly followed her courting.

As the collared doves, they also ate seaweed, drank seawater (!) and waded in the waves. Don't take my word for it and watch the following clip.

Saturday, 13 August 2016

Woodpigeon mating

Although the Woodpigeon must be one of the most abundant and familiar British birds, a few days ago I was lucky to watch their courtship and mating at very close quarters, when a pair landed on the garden fence. I should have taken a video, but instead I ended taking a series of photos, which don't cover the full sequence. I saw, but did not photograph, the initial courtship feeding.
1. The male (on the right) had just fed the female, both move the bills, like swallowing. They are right next to each other and excited, note the contracted pupil in the male. The female sits down, crouching, inviting copulation.
2. The male mounts the female, balancing with wings open.
3. The male stabilises on top of the female, which remains motionless, with  wings spread (to make male balancing easier?).
4. Copulation, male flaps for balance, female leans forward lifting tail.
5. The male jumps onto the left of the photo, both partners (which are extremely alike in colour and size) fluff their neck patch and bow their heads in what looks like an aggressive display. These are woodpigeons in all their splendour, what amazingly beautiful birds they are!
6. The female actually turns away from the male, not a brilliant shot but shows how the neck patch feathers are raised. The pupil is very contracted.
7. The male remains in the post-copulation display.
8. Both pair members come together again and preen (I think the female is now on the right, and shows the initiative in caressing the male neck and head area).
9. The caressing carried on for a while.

Wednesday, 10 August 2016

The beachcombing crows

Crows are opportunistic and generalist feeders and live in a wide diversity of habitats, from woods and cities to the sea shore. They have to go through a period of learning from their parents how to forage, in particular about the best way to obtain resources for each habitat. I've been staying by the sea on the south coast on the UK for a few days, and I've spent a fair amount of time watching a family of Carrion Crows with three young. They often feed on the beach, visiting especially at low tide. The young appear capable of finding their own food, but they still regularly beg for food from their parents. The beach crows probably get live invertebrates beachcombing from the tideline, but they will also scavenge wash out crabs or fish, in competition with the local gulls.
  The adults, although tolerating the young nearby and allowing them to follow and watch what they eat, lunge to them aggressively if they are harassed too much.
Two of the young flanking one of the adults, note the size difference.

The adults are moulting and are, to put it mildly, not looking at their best. One of them is almost bald: many instances of sticking their face into the open bill of their nestlings (if, as I presume, it's the male, he will have also fed the incubating female) for a few weeks during the breeding season have taken its toll on its head feathers.
The bald adult, possibly the male.
Young are smaller than the adults, with legs that look long for their bodies and wing feathers that are not fully grown. They have a brown sheen to their head feathers and have pink mouths, obvious when they beg. This one has also some wing feather discolouration probably due to some nutritional deficiency.

The young, on the right, begs for food from both adults.

 The young crows spend some time away from their parents, walking on the beach, picking seaweed or turning a little stone to peck underneath.
Young crow watching a young Herring gull, from the family they share the beach with.

One of the young crows picked on the empty shell of a spider crab demonstrating its deft foot use (above). Another got a small crab this morning, and a Herring gull chased him. The crow persevered and ate his crab. But as soon as one of the adult crows gets something, the young crowd around.

One adult (the one not bald, which I will regard as the female) crow stole an egg from a pigeon's nest. As she landed on the beach, carrying the egg deftly in her bill, and still dragging some nest material, the three young immediately surrounded her, begging. The adult did not want sharing though, she wanted the egg all to herself. She walked up and down the beach trying to find a suitable spot for dinner, but the young followed her closely. Eventually she placed the egg on a rock, opened it and started lapping the contents. The young harassed her no end, even pulling at his tail feathers, and they only managed to taste the egg after a kerfuffle when one of the young managed to grab the egg and the adult chased him and put him down with her foot. You can watch a short video of this here: