birding-aus Fw: Are birds affected by daylength?

To: <>
Subject: birding-aus Fw: Are birds affected by daylength?
From: "G Glass" <>
Date: Thu, 11 Feb 1999 16:34:20 +1000

Further to Steven Clarke's theory -

That could explain how it was for the month before about Christmas our dawn
chorus at Gowrie Junction (NW of Toowoomba, Qld) was deafening,
particularly with Figbirds (and 23 other species) while early in January
the din was considerably less, though the number of species not at all

Gloria Glass

> I don't think Christmas is an important event for birds (geese, turkeys
> excepted) but it occured to me that Dec 22nd is the summer solstice - the
> day when daylength is greatest and the beginning of shortening days.  Is
> this the trigger for many species to stop breeding activity (calling and
> display flights)?  I know daylength (or nightlength) is important for
> plants and I'm sure that I've read where it is a probable trigger for
> migrating birds but the daily change around the solstice is so small
> (seconds) that I find it hard to believe birds could detect it as
> precisely as my theory suggests.
> I welcome any discussion on this but please - not too technical. 
> Cheers
> Steve
> ------------------------------------------------
> Stephen Clark

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