This raises a question about migration 'triggers,' so I'll ask it: I've read in the past that what drives Northbound migrants to start migrating is not the weather, which is too variable, but the number of hours of daylight. That was asserted as the birds' sense of calendar, and it makes perfect sense.
BUT... if the summer solstice in the Arctic is when they are due to start their Southbound return, how on earth do they know when it is? Dave Cameron Denver -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to cobirds+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/8013063a-dcb2-4868-88b8-28941b26175eo%40googlegroups.com.
