Lecherous Sparrows

Chaucer in Canterbury Tales, compares his Summoner's concupicity to sparrows. The summoner, we are told is "As hoot he was and lecherous as a sparwe" (General Prologue l. 628). It turns out Chaucer was on to something.

The saltmarsh sparrowCredit: Wolfgang Wander (Ammodramus caudacutus), a native of the coastal marshes of Connecticut, is a small, slightly stocky but fairly typical looking sparrow. Saltmarsh sparrows are considered songbirds, but their precarious habitat at the edges of tidal marshes seems to have affected their behaviors. Unlike most songbird species, they do not mate for life; nor do the males participate in chick rearing or feeding. Because of tidal rhythms, their nests are endangered by high tides every four weeks.

Ornithologist Chris Elphick of the University of Connecticut, has just published his research on the saltmarsh sparrow's sexual practices and fecundity. According to Elphick's research (published in the current issue of Auk), at least 95% of the saltmarsh sparrow females he studied mated with more than one male, so that in a single clutch of eggs, the chance that any two chicks share a male progenitor is only 23%. Moreover, one in three nests had a different male parent for every chick. The average clutch of hatched eggs had more than 2.5 fathers.

Elphick suggests that given that chick-rearing takes roughly four weeks, it is an evolutionary positive for the saltmarsh sparrow species as a whole, to have as much genetic diversity as possible in a given clutch, since their is a strong probability of several nests being destroyed completely at the highest tide.

You can read more about Elphick's research here and here, and about the saltmarsh sparrow here.