Greenfinch (Carduelis chloris)
Greenfinches are at their most obvious in the spring, when the males utter their canary-like trilling songs from the tops of trees and bushes; the usual run of phrases is regularly interrupted by an emphatic wheezing note, sounding a bit like the word “Green”. Every so often the males break off from perch-bound singing to launch into a song-flight, in which they flutter at about tree-top height with heavy wing-beats, pitching to and fro and often describing circles or figures of eight.
Recent studies have shown that the Greenfinch’s pairing system is quite complicated. Although monogamy could be considered the rule, about a quarter of males in a population may be polygynous, with two or even three mates each. This leaves some males unpaired, and it is not uncommon for them to display to attached females, and even help with feeding the young. Later on, quite a high proportion of such helpers pair up and breed with the female concerned when they opportunity arises, as if being rewarded for their efforts.