A recent paper published at nature.com
revealed how fickle the female Lark Buntings are when it comes to picking a mate each spring. It is generally thought that females of most bird species select their partner based on a few traits that lead to that trait being exaggerated in the male. A good example of this is the peahen picking the peacock with the gaudiest tail year after year which drives natural selection towards even larger and gaudier tails (providing they aren’t so large that it makes them too easy for a fox to catch.)
Lark Buntings on the other hand, seemed to select for varying traits from year to year. In a 5-year study in Colorado, scientists found that females first selected for larger beaks, then the next year selected mates based on how dark their plumage was. Another year the females selected mates by body size, preferring the smaller males and the next year the trend was the reverse, with the larger males being sought after.
The researchers believe that the females are taking into account the current circumstances regarding the breeding site and selecting a male based on who will be best suited to those circumstances. They also think that this behavior will be found in other species.
These are very interesting findings and the next step that I see would be to relate the surrounding environment to the mate selections of the females and determine what cues the females are processing to make their decision regarding what trait to select for. It might also indicate that these birds may be more adaptable than once thought if they can so quickly change what traits they consider desirable.