Wednesday, January 03, 2007

Hardest Working Bird in England

Meet erithacus rubecula, also known as the European Robin, which also happens to be Britain's national bird.

I'm writing about this bird today because a pair of sparring males kept me awake for more than an hour last night, starting at around midnight.

Clearly they were confused--did they think it was dawn already? Or did something upset them? Bursting with curiousity, I did a little research this morning.

First, I learned that robins are one of the only birds to sing year round in England. According to the Royal Society for the Protection of Birds, they're usually the first birds to start singing before dawn, and the last to stop in the evening. Apparently, street lights and other disturbances can trigger singing in the middle of the night.

But there were definitely at least two birds singing--one in the tree right outside would let out an impressive song and then another in the distance would answer just as keenly. They continuted this volley for some time (I eventually fell asleep) and the singing matches have continued pretty intesively all day today. Investigating further, I learned that in mild winters (such as this one), the mating season--a time when robins sing their little hearts out--can start as early as January.

So that must be what is going on!

Apparently, the male robin sings during mating season for two reasons: to establish and defend his territory, and to show prospective mates what a prize catch he is. The territorial songs differ dramatically from the mating songs. I came across this explanation of the intricacies of mating songs which is so fascinating I'm providing an excerpt:

Singing is an honest indication to a female of the males quality and fitness because it is an energy intensive activity. If a male has the excess energy to sing a long, loud, complicated song after a night without food, he must be a good, strong forager and live in a productive territory. This is what the females want. A weak, hungry bird will not have the energy to sing such an impressive song.

Many birds amplify their song by singing on high, exposed perches, however this also makes them visible to predators. By avoiding these predators, males can further show females their strength.

During the dawn chorus, female birds listen to each song and visit each territory before deciding on a male to mate with. As they prefer males with the most complicated songs, the males constantly develop and re-develop them. European wrens for example, have songs that contain over 700 different notes per minute and can be heard 500m away.

Imitating another species' song will also increase repertoire and complexity and show the female that a male has survived enough breeding seasons to have heard these other songs. Some migratory birds even imitate international birds. Marsh warblers may mimic the sounds of 70 or so species, telling the females where they have spent the winter.

Can you imagine? I had no idea there was so much going on in all of those songs, or that it was such exhausting activity. I suppose I better start re-hydrating more mealworms.

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