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:

Thursday, 4 August 2016

Visiting the swift tower

Yesterday we did a stop in Oxford on our way south of the UK. After lunch, we quickly popped by the Natural History Museum. This magnificent building holds the swift breeding population that have been studied for several decades. The nests are in adapted nest boxes, which have access from the inside of the building for ringing in the main tower.

A detail of the tower showing the entrances to the nest boxes.

It is quite late in the short Swift breeding season and many fledglings and adults have already left for their African wintering quarters. Every time I see a swift I think it could be the last of the year, so I was not too hopeful of seeing any around the tower.

Birdtrack reporting rate of Swift, showing the main breeding season from May to August.
Then the website revealed that the last Swift nestling in the tower was born a couple of weeks ago (18th July) and hadn't yet fledged. The Museum has set up a live webcam in which you can follow one of the nests. The webcam is now set up onto the latest born nestling. I watched the nestling for a while today and got a couple of screen grabs.
An adult likely after feeding the chick, on the foreground, and the well grown nestling. Young have pale-rimmed feathers on their face, unlike adults.
The youngster resting. It spent some time flapping its wings and grooming. Although is quite feathered, its wing feathers are still quite short. The wing feathers will need to reach beyond the end of its tail before it can leave the nest. You can also see a rejected egg just outside the nest.

As we walked onto the square in front of the Museum and just after taking a few photos, a lone Swift flew overhead. Not the mad noisy chases of dozens of Swifts that usually surround the tower at the peak of the breeding season, but a great end of a lovely visit. 

Monday, 18 July 2016

Blackbird anting

This morning, on my way to work, I noticed a Blackbird behaving strangely by a kerb. When I looked closer I realised that it was 'anting', a behaviour involving the use use of ants by birds. The Blackbird had its tail and wings spread, squatting - probably on top of an ants nest - and the ants were climbing on the birds feathers.  The blackbird was rubbing its wings, coming back to the same spot. An ant run by the back of its head and the blackbird wiped it off. You can watch a short clip of the behaviour.

Anting is thought to aid in cleaning or disinfecting the bird's plumage. The bird would be using the ants as tools, as ant's secretions, including formic acid have known bactericidal, insecticidal and fungicidal properties. The ants would behave agressively and defensively if they are picked up or rubbed by the bird or if the bird is disturbing their nest.

Blackbirds, other thrushes, starlings and corvids use anting. Some of the species sit on wood ants nests, or even apply individual ants on their plumage. Some bird species use a similar behaviour with millipedes, which also produce strong chemical secretions.

I think it is unlikely anting is a learned behaviour, as it is quite rare. I wonder if the ant's frenzied activity around nests today - it was flying ant day in Hull - stimulated the Blackbird to engage in anting behaviour.

More information
See this post at my other blog on birds and flying ant day

Tuesday, 10 May 2016

Collared Dove exhibition flight

Collared Doves have a extraordinary behaviour, their display flight. As males incubate during the day - between 10 am and 4 pm -, and females by night, males are most vocal and active advertising their territory in the early morning and in the evening. Males call their repeated three-note phrase from a prominent perch an aerial or a tree top in the vicinity of their nest. At the end of their call they pause and then launch themselves into a display of pure flight power: climbing almost vertically up to 10 m into the sky, and then gliding down in a broad, long spiral, with wings kept spread pointing downwards, and tail fanned, to finish in the same or nearby spot, sometimes calling a mute trumpet-like landing call. The wing flaps make a soft whistling noise. This sequence can be repeated several times in the early morning and evening. This morning I watched this male sitting on a church top calling, and managed to get the initial jump of the perch into his display flight.
You can watch a slow motion clip of the display flight by redjered here