Sunday, 28 April 2013

House Sparrow communal courtship

 ResearchBlogging.orgHouse Sparrows are quite vocal birds. In spring, a house sparrow colony is hard to miss, with males advertising their chosen nest sites to potential males by chirping and posturing, but mainly by their peculiar communal courtship. Communal courtships start when a fertile female not guarded by her mate flies by an unmated male, the male then will pursue her while chirping and displaying persistently soliciting copulation. More males usually join in the female chase and courtship in a cacophony of strident chirps. The female is far from passive to the male's attentions, and often lunges and pecks at the males (photo below), which seem quite unfazed. Forced copulations - and also accepted copulations - occur during these communal courtship displays.
 Male sparrows with large black chest badges are more dominant in the sparrow colony. They guard their mates during the fertile period - around the period when egg-laying is taking place - and copulate with her frequently. But males with large, in addition, join communal courtships more often than males with small bibs, so these dominant males may achieve paternity both though their mate's offspring, and through extra-pair copulations.
 Today, in a local farm, I managed to get these shots of communal courtship in House Sparrows. Two or three males were harassing a female, and she managed to peck one of the males (below).
More information

Moller, A. (1990). Sexual behavior is related to badge size in the house sparrow Passer domesticus Behavioral Ecology and Sociobiology, 27 (1) DOI: 10.1007/BF00183309

Saturday, 27 April 2013

Nectar feeding Blackcap

ResearchBlogging.orgYesterday 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