Monday, 17 December 2018

Grey Wagtail feeding

Grey Wagtails breed in upland streams and rivers, but they are common passage and wintering birds in urban waterbodies, from small ponds to lakes. I watched one today in a local park,. Despite their name, they are surprisingly yellow, in the low winter sun this one shone very bright.

Grey Wagtails don't move much away from water, and often feed right at the waters edge picking tiny flies, beetles and other invertebrates, while wagging their long tails up and down. Today I was surprised by the behaviour of this wagtail when feeding on leaf litter by a puddle, as it was energetically lifting leaves and looking under them like a blackbird does.
This clip shows the behaviour:

Monday, 3 December 2018

Watching Waxwings

Yesterday, I got up early and had a short drive to a local supermarket to watch some Waxwings that had been reported. Waxwings are irregular winter visitors to the UK, especially to its eastern side, and are most likely to arrive to a supermarket car park near you. A lovely mild morning with sunny spells and a light wind, I walked around the quite empty car park checking the rowans, a couple of small ones still with berries. two Woodpigeons and a Blackbird were feeding on them, but no trace of Waxwings.
Blackbird sitting on a rowan still laden with berries.

Suddenly, a flock of six Waxwings appeared silhouetted against the rising sun and landed on the tree in front of me.
The safe tree
Almost every time I've seen Waxwings, they alternate between bouts of frantic berry feeding and resting in a tree nearby. It's not just any tree, it is a particular tree. This tree attracts them like a magnet and they appear not to settle anywhere else. This time their safe tree was an ash, the tallest tree in a row on a rise by the road separating two supermarket car parks. The Waxwings spent a few seconds feeding on a yellow-berry rowan, and then they flew back to the top part of the ash tree, where they spend most of the time. Other times the flock would fly towards a rowan and return to the safety of their tree even before landing. They are extremely watchful, looking up nervously every now and then with bouts of preening, resting and calling.
Their quiff-life crests rise or flatten with their mood (compare the top shots taken a few seconds apart), sometimes becoming ruffled with the breeze. They are not particularly wary of people, some photographers assembled just underneath their tree, pointing at them with their cameras, walking right under them, and they paid no attention.

Birders and Waxwings on their safe tree.
Instead, they are watchful of predators. Being small birds, similar to starling in size, they would be easy prey for Sparrowhawks. Indeed, later on, when I go for a wander in the area, I see a Sparrowhawk flying past chased by a flock of starlings.
This is the only shot I got of the Waxwings in the rowan where they fed.
Decision making
When to go to feed? It was interesting to watch the individual Waxwings on the tree. At some point one of them appeared restless, and would fly from branch to branch around the others - which were preening or resting - or it would fly up and away from the tree a short distance, and if the others didn't follow, it would return. This individual appeared to be rallying the group to go and feed.
 Earlier in the week there had been nine Waxwings about, then the six yesterday. Today just two remained. Two Mistle Thrushes sat on a lamppost, guarding the rowans, so not sure the Waxwings will stay much longer. The two waxwings sat close in the tree and billed each other briefly, maybe passing some food?
Early arrival of Waxwings indicate an irruption year, so I do hope there's more opportunities this winter to catch up with them.

Thursday, 29 November 2018

Bullfinches eating Guelder rose berries

A group of Bullfinches were feeding just outside Dalby Forest visitor centre this afternoon. We watched them from a window, just over them, and they seemed quite unaware of us, providing a great opportunity to watch this usually shy bird in action.
 Bullfinches are seed predators of many fruit trees. Blackbirds, Thrushes and Woodpigeons are seed dispersers, they eat the berry whole, digest the pulp and the seeds drop to the ground, undigested and prepared to germinate. This is the reason trees and bush species evolved fruits, as the way to disperse their seeds. In contrast, seed predators discard the flesh and eat the seeds inside each fruit. Many finches, like Hawfinches, Greenfinches and Goldfinches, are seed predators too.
Bullfinches favourite seeds include Honeysuckle, Rowan, Elder, Whitebeam and Blackberries, each ripening at different times of the year. Today, they were feeding on the bright red berries of the Guelder Rose, a late fruiting small tree. In their fantastic book "Birds and Berries", Barbara and David Snow document how bullfinches are one of the main seed predators of Guelder Rose.
 The bullfinches stretched to reach the berries (top shot) and used two techniques to get at the seed. They either opened up the fruit and picked the seed, leaving the flesh hanging from the bush or picked the berry and deftly extracted the seed. They will even hovering in front of the bunches of fruits to reach the most difficult ones.
A male picks a berry.
Female extracting a seed...
...and dropping the flesh.
There were not only bullfinches at the tree, a lone Robin, a seed disperser, was feeding on the berries, so even though there was a lot of seed predation going on, it's likely the Guelder Roses will manage to get some of their seed seeds to germinate.

More information
Snow, B. and D Snow 1988. Birds and Berries. T & AD Poyser. 268 pp.

Saturday, 24 November 2018

A flock of Goosanders

I went to a local park today for a walk and found a flock of Goosanders in the lake. It is a fishing lake, frequented by anglers in the summer, but it was quiet today, and the Goosanders, had the fish to themselves. Goosanders are hard to count when they are fishing, as they are constantly diving -often one after the other- but I managed to count nine males and six females. I stayed away from the shore, half hidden on a tree trunk, as these ducks are wary of people. Soon after I started watching them, a male caught a large fish, another goosander followed it, interested, but the first one managed to keep it and swallow it.
Drake Goosander with fish.
 The Goosanders kept in a tight flock, when the fishing session was over they spent some time preening and flapping their wings and doing some exaggerated head shaking, which might also be related to courtship as the movement helps show their showy hairdos.
The fishing lake.
Shaking head looking straight up.
Drake Goosander.
The same drake. The photo shows the neck striations that form a 'bun' at the back of their head. 
Then a female went to the shore for a rest and a preen and one by one, several of the others followed her there, jumping awkwardly onto the edge. Their legs shone bright orange like Mallard's.

Tuesday, 29 May 2018

Moorhens building a brooding nest

Yesterday I popped in my local park and I watched three just hatched moorhen chicks with an adult. This pair of moorhens usually nests high in a willow tree, in the main fork of the trunk. I have seen one of the adults several times up the tree in the last few months, but I failed to find the nest. Today I went to the park again to check on the moorhens. I was surprised to find the female brooding the chicks on a new nest by the island (top shot), which wasn't there yesterday. The male was busy bringing her sticks and leaves. He would find a stick or leaf on the ground, run to the shore and swim as fast as he could to the nest and pass the material to her partner. The female was fluffed up and looked double the size of her partner. She was sheltering the young under her wings.
 If I hadn't seen the chicks yesterday I would have assumed the moorhens were nesting anew. Once the chicks leave the nest in the tree for the first time, presumably jumping to the ground or the water, they can't climb up the tree again. These adults are being very resourceful by building a second brooding nest for the chicks to shelter when they are still small and cannot thermoregulate properly.
One of the moorhens with chick yesterday.
The moorhen sits and the chicks get in to be brooded one after another. She pulled a few small twigs towards her as she was brooding them (photo from yesterday).
Male coming in with a stick.
A rotten leaf will do as nest material too.

Thursday, 19 April 2018

Gulls mobbing Buzzard

From my office I hear several Herring Gulls start calling plaintively, kyeoh! kyeoh! a loud, far carrying call that I associate to buzzards overhead. I looked through the window. The local Carrion Crows had assembled atop a large poplar, watching nervously, calling and displaying wing shuffling and tail fanning.
A dozen gulls soared and called - all the local Herring gulls - slowly assembling and ascending on the thermals. Then I see a Buzzard, soaring higher. The gulls didn't reach the buzzard's height and it eventually drifted away and the gull calls died off.
 Gulls often alert me to raptors. A couple of years back it was a Honey Buzzard, migrating over town. I pay a lot of attention to the gulls alarm call since then!
 Later, at home, the scene appears to repeat itself. Alarm calling gulls. I grab the camera and go out into the garden. Two Lesser Black-backed gulls are mobbing a Buzzard.
 This gull alarm call is persistent and sounds distressed, it is hard to ignore. It seems to attract other gulls too, who soar and chase the potential predator. I wonder if it is how young gulls learn to identify the predators they are likely to come across in their lives. Crowd knowledge of the enemies, initiated by older gulls with previous experience, who in turn learned it in their youth. Immature offspring of the gulls initiating the mobbing are likely to be around. The adults could be 'teaching' young about potential predators and the young are likely to benefit from this at some point in the future. This is a hypothesis called 'cultural transmission of mobbing' which was explored in some experiments by E. Curio and collaborators in 1978. They showed that exposure of a novel object to a 'naive' Blackbird at the same time a 'teacher' blackbird is mobbing results in learning to mob the new object (in one of their experiments a colourful bottle). This teaching could be passed through six rounds of learning in which the learner becomes the teacher of a new bird, and so on. The fact that enemies often have to be recognised culturally was put to a sad test when captive reared endangered Hawaii crows (or Alalā) were released into their natural habitat. The last wild Alalā had died in 2002. Two of six newly released birds were predated by native hawks, to which the captive reared birds were completely naive in the first week after release. The conservationist recaptured the surviving birds and started an intensive 'predator training' program in which the captive crows were exposed to hawks calls, hawks flying overhead and simulated hawk attacks. Hopefully the savvy crows will do better when they are released next.
This time of the year there seem to be a passage of migrating or dispersing Buzzards over the city. The gulls are breeding, probably incubating now, and a buzzard could be a predator likely not for them, but for eggs left unattended or young chicks. It makes sense that the gulls see off the potential predator.
I got this short clip from the garden:

More information
Curio, E., Ernst, U. and Vieth, W. Cultural transmission of enemy recognition: one function of mobbing. Science 202, 899–901 (1978).

Different gull calls: here.

A blog post including some great photos of Herring gulls mobbing a Buzzard

Sunday, 28 January 2018

Mute Swans drying and tucking foot

Mute swans often stick one foot in the air as they swim (top shot) easily steering themselves with the other foot. I had often wondered what the purpose of this habit was.
  The two Mute Swans in my local park have afforded close observation in the last couple of months. Last week I noticed that sometimes they have one of their legs tucked under their flank feathers, virtually invisible, only a bit of the 'knee' showing, while swimming with the other leg. This behaviour probably results in keeping one leg quite warm under the plumage.
Yesterday I put both behaviours together by watching how the young swan took one foot out of the water, shook it and left it out for a while. Then it behaved like it wanted its leg dry before tucking it under its feathers: it tucked his leg under the feathers, but seemed not to be happy about it and it stuck it out again and shook it a bit more before finally tucking it in for good.
 I had noticed that cygnets, even before they have feathers, have this habit of tucking a leg out of the water over their body. I just had never realised the adults would do it too, preceded by the leg-stuck-out while drying.
This behaviour has also been reported in other swan species and although thermoregulation seems to be the underlying reason, both cooling and drying/warming have been proposed as explanations for the behaviour.
 The next series of photos illustrates the sequence of behaviour.

The following photo is from 21 June of 2015, taken in a local fishing lake. A young downy cygnet a few weeks old. You can notice how its right leg is tucked by its body, outside of the water, while it preens. When it grows feathers, the same position results in a leg completely covered with feathers.

More information
Why do some swans only paddle with one leg, with the other leg tucked up under the wing?

The Whooper Swan. Here. p 93-94.