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[Sparrows] In which Shane is a better collector than vet

December 6, 2012

[This is the eleventh in a series of posts on sparrow nest-monitoring over the 2012-2013 Austral spring and summer.]

Today, in my home city, tornadoes have left three people confirmed dead. I decided it was a good day for staying indoors.

Weather aside, sparrow monitoring is proceeding very well. I’m up to 18 monitored nests, with ten actively incubating. Having an assistant to hold the ladder has meant that I can get to some awkward nests and bumped up my sample size, although it will leave me in a tricky situation if I stop having an assistant.

In the last week, several of my hatchling-bearing nests have dropped hatchlings. In one of those cases, the hatchling was still alive.

Now, what does one do with a live, dropped hatchling? The old story that birds reject hatchlings that ‘smell like humans’ is false – cross-fostering of chicks is a widespread and highly successful conservation technique, and cross-fostered chicks are all handled by humans. In reality, chicks are mainly rejected from nests because of siblings competing for food, by parents who realise that they cannot gather enough food to feed all their offspring (see Terry Pratchett’s ‘Dreadful Algebra of necessity’), or by brood parasites like cuckoos, which have a habit of throwing out all the other nestlings in a nest.

In all those cases, there is very little point in returning the hatchling to the nest – the siblings, parent, or brood parasite will just throw them back out. I attempted it on the grounds that the nest might have been damaged by my monitoring of it (my hands are wider than a sparrow, so some nest openings have been forced to be a little wider too), and the nestling may not have been deliberately rejected. Fortunately, this was not an experimental nest, so I was not worried about messing up the experiment.

No luck. I found the same hatchling on the ground again the following day – surprisingly still alive, but with some nasty peck-marks about its head. So, a plan was hatched to to try rehabilitation. I had with me a trained wildlife stabiliser, Google, and a Shorebird Centre full of mildly-puzzled interest: surely we could come up with something, and I could cross-foster the chick out when it hit fledging time?

Nope. It was dead by morning, in spite of successfully eating the hand-caught insects and mushed-up bread gruel. It turns out wildlife rehabilitation is hard.

Silver lining: I now have a dead sparrow hatchling from a monitored nest, which I have preserved in ethanol, and for which I know the laying date, hatching date, and death date. This kind of metadata could be very useful to researchers looking at developmental biology, or the specifics of hatchling-rejection, and the Auckland Museum has accepted the specimen. In fact, I have two such sparrow hatchlings, because I found another hatchling dead on the same day I found the live one. I may suck at rehabilitation, but I’m still pretty OK at data collection.

Sparrow hatchlings in ethanol

Biological specimens in ethanol! Just like old-timey natural historians!

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From → Scientist

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