[mbaldw]

Hi Hedgehoggy,

I was shocked to find my post had been resurrected, but more than pleased that my curiosity has now been satisfied.

Heh! I don't often browse the bird forum but I was looking for another post and came across your question about Tawny owls. It's interesting that despite the plethora of generally-published (i.e. in books, rather than journals) material on Barn owls, there are so few on Tawny's (the excellent studies by Lindhard Hansen in 1952 and Manfred Melde in 1989 in notwithstanding).

I’ve heard, what I’m almost certain to be, the parents communicating with their young.

Really? Awesome. What sort of sounds are you hearing? Very young Tawny nestlings make a sound described as "bi-bi-bi", which changes to "psji-ii" (a kind of hissing sound) then to a more squeaky "siii-siii-siii"; recently-fledged young produce a "ti-sweep" or "ti-swerpt". In his book Owls Chris Mead points out:

"One of the least enduring habits of the Tawny Owl is the persistent squeaking of the newly fledged youngsters for food. This has variously been described as a 'rhythmical and monotonous series of squeaks' and 'an infernal racket'."

This is all to do with the parent's feeding strategy whereby they can return at any time with food, so the youngsters yell almost constantly to attract their parent's attention.

There was a recent post where two posters were hearing Tawnies calling during the daytime, one of which hears the Tawnies all throughout the year during the daytime. I’ve personally never heard a whisper from a Tawny during daylight, so was curious (again!) as to your views on this diurnal calling phenomenon throughout the year, not just the breeding season?

This is very interesting. I’ve never heard a Tawny calling during the middle of the day, but I’ve read accounts from several people who have. There was a discussion about this on a birding forum on which I lurk a couple of years ago and the general consensus was that the OP was either hearing a Jay ( Garrulus glandarius) -- which can apparently produce a superb mimic of a Tawny’s call -- or were in a high density Tawny area (high density = space at a premium = more territorial calling). Whatever the reason, it doesn’t seem an uncommon occurrence and even the RSPB, in their brief bio on the Tawny, mention that it may call during the daytime, although they don’t pursue the subject further.

The BTO conducted a study between October 2005 and April 2006, which collected data on Tawny owl calling habits. Unfortunately, I’ve only seen Steve Freeman and Mike Toms’ summary (published in their Bird Table magazine) and it doesn't mention daytime calling. Nonetheless, I'd wager the full dataset makes interesting reading.

Arguably, from the scientific data I've seen, Tawny owls are probably better off keeping stumm. Between 1998 and 2002, a collaboration between scientists at the University of Copenhagen and the University of Lund studied the habits of Tawny owls in the Gribskov Forest, Denmark. The biologists found that of the 15 owls in their study site that died of natural causes, 11 were nailed by raptors (namely goshawks, Accipiter gentiles). It seems that prior to meeting a goshawk, juvenile owls perched out and roosted in open spaces; after encountering a goshawk, however, the birds roosted in less exposed places. The authors concluded that:

“ depredation [an attack by a predator] by diurnal raptors is the main factor shaping the diurnal behaviour of tawny owls.”

If we consider this Danish site to be representative, one might expect owls to keep quiet during the daytime where potential predators (or mobbers, which as well as being a pain can also advertise your presence to prey and predators) might hear them. With this in mind, it doesn't seem unreasonable to think that, in a relatively enemy-free space, they could perhaps afford to be more vocal during the day.

Anyway, that was kinda a long-winded way of saying that I don't really know why they sing during the day!

Cheers,
Marc.