nest box saga continues

[watervole]

At least one blue tit is still definitely visiting the nest box regularly. I sighted him/her with a caterpillar this morning and several time later during the day.

I've seen the great tits as well going in and out.

Has anyone ever heard of two species sharing a nest box?

Blue tits and great tits sometimes flock together in the winter (they don't compete directly for the same food as they tend to feed at different heights and I guess more eyes are better for spotting predators)

Comments

[lizblackdog.livejournal.com]

I have a vague feeling that I've read about such things happening, but I'm damned if I can find any actual references.

however, if they're not competitors and they're not in the habit of attacking each other that certainly makes it possible. hope the blue tits come off OK!

[temeres.livejournal.com]

Tits regularly flock in winter, not just Blue and Great together but - depending on the range of species present - Coal, Long-tailed, and/or Marsh/Willow Tits, along with Treecreeper, Nuthatch and Goldcrest. A winter walk through a wood can be more or less birdless unless you bump into one of these roving bands.

It's not so much feeding height that allows them to feed in a party as the difference in prey species. Research into Great Tits has shown that males and females have slightly different beak sizes, and thus gives them a different prey range. Since a Blue Tit beak is much smaller than a Great Tit beak, it's reasonable to assume that Blue Tits are feeding on something else entirely, and hence not competing with the Great Tits (and other species) they associate with. Research on Galapagos finches suggests that a difference in beak length of as little as half a millimetre can have a profound impact on the range of exploitable food resources (and when food is scarce, can mean the difference between life and death).

The winter flocking is probably an anti-predator thing. Not so much more eyes, though. Just a better chance of not being the one that gets snatched up by a Sparrowhawk. There's probably a trade-off between flock size (larger flocks are more likely to be noticed by a predator) and escape probability, though I haven't heard of any research into that.