Redpolls and Goldfinches feeding on Sycamore aphids

 I'm used to finding Lesser Redpolls in the coldest days of winter, when small groups feed quietly on birch catkins. Learning their cheerful 'chi-chip' call, sharper and less liquid than Greenfinches, has helped me detecting them as they move around the city. I was surprised to hear their flight calls amongst a flock of roving Goldfinches at my local cemetery, a misty but mild morning. I trained my binoculars high up on the Sycamores and spotted them, apparently gorging on the last fat sweet aphids still under the Sycamore leaves, together with the Goldfinches. Some Chaffinches and Blue and Great tits were also on the sycamores, but I'm more used to these species feeding on insects. The distance and the poor light didn't make for great photos, but I was pleased to record a behaviour I had never seen before for both Redpolls and Goldfinches.

Sycamore aphids.

Redpoll gleaning sycamore aphids.

Lesser Redpoll.

Lesser Redpoll.

Goldfinches and sycamore aphids.

The summer Blackcaps

At the end of April, the arrival of migrant Blackcaps is marked by their beautiful fluty song. Males arrive a few days earlier than females and settle in their breeding territories. I heard the first one in the park on the 19th of April. Blackcaps usually sing from cover in trees and bushes, and the rapidly sprouting leaves will make it more difficult to spot them singing as the spring avances. Today I found a female in the territory where the male had been singing. She was very busy in a tall Sycamore tree, Acer pseudoplatanus, picking aphids from under the leaves, stretching and balancing on the fine branches. The male wasn't far, singing and feeding on aphids like her.

The female feeding.

Note the two aphids on the main veins of the leaf near the male's bill and...

...a few seconds later they are gone.

A short clip of the male feeding.

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.

Nectar feeding Blackcap

Yesterday I heard a male Blackcap singing on my way to work. Although it was high on a tree, luckily, I had a small pair of binoculars with me and I found him on a Sycamore in bloom. While I watched it, the Blackcap alternated singing and clearly drinking from the Sycamore flowers, in one occasion clinging upside down from a branch like a tit to reach them. It is well documented that several European birds, especially warblers, regularly drink nectar (I have posted on Blue Tits feeding on Mahonia nectar before in this blog). I could only take some distant shots of this behaviour, and when I got back, I did some research on the nectar feeding habits of the Blackcap.
 The Blackcap is actually one of the most nectarivorous European warblers. Nectar feeding in warblers is most common during spring migration, and has been documented in many stopover sites. Blackcaps often have stained faces due to their flower feeding habits (you can see some examples here and here. This can result on the formation of a 'pollen horn' a matted mass of nectar, pollen and feathers around their bills. Given that their long, thin bill leaves flowers intact after feeding, that they visit many flowers and the presence of pollen on their faces indicating regular contact with the flower's anthers, it is not surprising that Blackcaps can also act as pollinators.
 Experiments on birds trapped during migration indicates that migrating warblers seem to prefer nectar to mealworms when both are offered simultaneously. Nectar feeding is not a last food resort for emaciated birds, but a valuable source of easily digested carbohydrates when birds have reduced digestive systems and high energy demands.
 Blackcaps feed on nectar from a large diversity of flowers, both native and introduced. From the references below, I have compiled the following list of visited plants, which also includes some Mediterranean plants that they encounter during migration, and the Sycamore too. I note the native status in the UK.

1. Goat Willow, Salix capraea. Native.
2. Sycamore, Acer pseudoplatanus. Native.
3. Oregon Grape. Mahonia sp. Ornamental.
4. Citrus trees, Citrus. Mediterranean.
5. Hawthorn. Native
6. Damsons. Here. Native.
7. Almond blossom. here. Mediterranean.
8. Scrophularia. Here. Four large flowered species. Mediterranean, Canaries.
9. Aloe arborescens This female has so much orange pollen on its chest that almost looks like a robin. South African plant widely introduced in the Mediterranean.
10. Anagyris foetida. The only documented native European plant that is exclusively pollinated by birds. Mediterranean.
11. Giant fennel Ferula communis. Mediterranean.
12. Brassica oleracea-group.

More information

Ortega-Olivencia, A., Rodríguez-Riaño, T., Valtueña, F., López, J., & Devesa, J. (2005). First confirmation of a native bird-pollinated plant in Europe Oikos, 110 (3), 578-590 DOI: 10.1111/j.0030-1299.2005.13877.x

Ford, H. (1985). Nectarivory and Pollination by Birds in Southern Australia and Europe Oikos, 44 (1) DOI: 10.2307/3544053

Schwilch, R., Mantovani, R., Spina, F., & Jenni, L. (2001). Nectar consumption of warblers after long-distance flights during spring migration Ibis, 143 (1), 24-32 DOI: 10.1111/j.1474-919X.2001.tb04166.x

Jacopo G.Cecere, Costanza Matricardi, Beatrice Frank, Simona Imperio, Fernando Spina, Gabriel Gargallo, Christos Barboutis & Luigi Boitani. (2010). Nectar exploitation by songbirds at Mediterranean stopover sites. Ardeola, 57(1), 143-157.

Ortega-Olivencia, A., Rodriguez-Riano, T., Perez-Bote, J., Lopez, J., Mayo, C., Valtuena, F., & Navarro-Perez, M. (2011). Insects, birds and lizards as pollinators of the largest-flowered Scrophularia of Europe and Macaronesia Annals of Botany, 109 (1), 153-167 DOI: 10.1093/aob/mcr255

Acrobatic Woodpigeons and helicopter seeds

The Woodpigeon stately presence might suggest that they are cumbersome birds, but Woodpigeons feeding on trees show that they are surprisingly acrobatic. Compared to their relatives the Feral Pigeons, Woodpigeons have shorter legs and longer tails, which give them more manoeuvrability when moving on branches. Today I saw a group of ten or so feeding on a cotoneaster tree. One of them swallowed one berry rapidly after another while keeping its head low by the bunch of berries, reminiscent of how pigeons drink, keeping their bills under water and swallowing the water directly. 

 Further ahead, three or four were eating seeds in a Sycamore - the ones that fly like helicopters - and having finished off the ones easy to reach, they were balancing and stretching at the end of branches to get at the remaining ones. The individual on the top shot had spent some time trying to reach a bunch of seeds beneath it. It then flew to the branch underneath and stretched its neck in the hope of being able to get them from there.