Friday, 4 September 2015

Hawks And Jays Made Hummingbirds Evolve

Black-chinned hummingbird (Archilochus alexandri)
Hawks Act as Unwitting Muscle for Hummingbirds | Science | Smithsonian

"My enemy's enemy is my friend" might be a cynical policy when it comes to government foreign relations, but it seems to work at least some of the time when it comes to genes (or maybe memes).

It has long been recognised by ornithologists that the nests of black-chinned hummingbirds in Arizona, USA, tend to be clustered around the nests of goshawks and Cooper's hawks, but the reason for this were not previously understood, and was maybe even somewhat counter-intuitive.

Now a team of researchers from Ecuador, Canada and the USA made detailed observations of the movements of hummingbirds, jays and hawks in the Chiricahua Mountains during three breeding seasons and have shown there is indeed a close correlation between the sighting of hummingbirds' nests and the presence of these hawks.

They have also shown there is a close correlation between the foraging behaviour of jays, the main nest predators on hummingbirds, and a prey species of these hawks, and the presence of these same hawks, more than a third of their foraging behaviour being conditioned by it.

Not surprisingly, therefore, there was a statistically significantly greater success rate for hummingbirds which nested close to hawk nests - an example of typical Darwinian natural selection.

Mexican jay (Aphelocoma ultramarina)
Regrettably, despite my subscription to Science, the journal Science Advances is not accessible to me, so I only have the above link to go by and don't have the specific details of this paper, not even the abstract. <rant>I think all the abstracts (at the very least) of scientific papers should be open access!</rant>

Mapping the flight patterns of foraging jays showed that when they were in the vicinity of hawks, they tended to fly up and over the territory to avoid the typical dive-bomb attacks of hawks. This created a virtual jay-free cone around the hawk nests and this is where the hummingbirds were most likely to be found.

So what we have here is a pattern of hummingbird behaviour which has evolved in the presence of both hawks and jays and a good example of how behaviour in an ecosystem is interdependent on the behaviour of other species. It's an example of how either genetically-moderated or learned (i.e., memetic) behaviour evolves in response to the environment in which the species finds itself.

I'd love to hear how an Intelligent (sic) Design creationists explains this one. Did this 'intelligent' designer really design hawks to eat jays just so hummingbirds would cluster around hawks to prevent their nests being robbed by jays? If so, where on Earth did this notion of intelligence come from?

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