birding-aus
I have long wondered whether (suspected that) owls are more easily detected
on moonlit nights. I have found forest owls (particularly lesser sooty)
more easy to find when the moon lights the forest (or so it seems - but i
don't have the data to confirm this). My thoughts (wild speculations) are
that: (1) hunting is easier for owls on moonlight nights so they spend less
time hunting; and (2) owls are not vocal while actually hunting, so
therefore they may be more vocal on moonlit n.; (3) the lighter it is the
easier it is to see them flying over or perched above the road; (4) walking
cross-country through the forest towards a screaming owl is easier with a
little moonlight. Of course, season, cloud, rain, wind, prey density,
forest type, terrain, search method and experience are but some of the
confounding characters. So, is it the behaviour of owls or of owl-seekers
that is affected by the lunar cycle?
Kavanagh & Peake (1993) found that moon phase had a significant effect on
detectability of White-throated nightjar and Owlet nightjar in Vic forests
but not on other species (Powerful, Sooty, Boobok Owls, Tawny Frogm.). This
surprised me. I can't recall other discussion of this subject in the
literature, but I've never looked for this specific topic.
Kavanagh, R.P. & Peake, P. 1993. Survey proceedures for nocturnal forest
birds: an evaluation of variability in census results due to temporal
factors, weather and technique. in Olsen, P. (ed) Australian Raptor
Studies. ARA, RAOU, Melb.
David James
PO BOX 5225
Townsville Mail Centre 4810
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