Martin migration question

[avesrun]

Everything I read states purple Martin's migrate during the day. Curious as to how this has been determined. Do the geolocaters record hours? It's interesting to me when i hear of a landlord waking up brightand early and finding Martin's at their site. Maybe Martin's are very early risers!
TimG

[Chuck4]

Everything I read states purple Martin's migrate during the day. Curious as to how this has been determined. Do the geolocaters record hours? It's interesting to me when i hear of a landlord waking up brightand early and finding Martin's at their site. Maybe Martin's are very early risers!
TimG

I have heard them out dawn singing at 3:30-4 am way up very high in the sky too. So I know they can fly then. It makes sense that they would migrate at that time too possibly.

[John Barrow]

Tim,
I think that martins are primarily day time migrants has been pretty conclusively documented by visual observation, as well as by radar. For example, roost documentation has shown martins arriving in a roosting area very late in the evening, with their departure in the predawn hours visible as expanding roost rings on radar.
I have observed a lot of migration along the Gulf coast with often large groups of migrating purple martins joining the local birds for an overnight stay. The next morning it's as if it all were a dream--the migrants are gone.
Yes, martins do leave the nest early--at least earlier than I am usually up to see them off. And dawn singing is a pre-dawn occurrence; it's been around 5 am when I have observed it.
I am unaware that geolocators have been used to determine the time of day that martins migrate. Generally geolocators show an approximate location of a tagged bird on a particular day. Generally for birds that migrate during the day that location would be placed at midnight, operating on the belief that such would best place that bird's location on that day. Likewise, for birds that migrate primarily at night, as many species do, the location would be determined at noon of that date, believing that would best pinpoint the bird's location at a time it had stopped migrating to rest and feed.
It is not abnormal for martins to arrive during morning hours. I think they often fly to the general area of their nesting colony location, check things out, perhaps catch up on feeding, interact with any area martins, and approach the colony when it is safe to do so. It is also not uncommon for earliest arrivals to visit the colony location, but roost in trees for several days before beginning cavity selection.

[avesrun]

Thank you John for that information. Bird migration in general has always fascinated me; the different forms of migration (complete, partial, irruptive, etc. ). They effects of food availability, day length and numerous other factors is intriguing.
Do the wintering Martins in Brazil and surrounding areas form similar pre-migratory roosts as they do prior to Fall migration? Thanks again for the information.

[John Barrow]

Tim,
Yes purple martins in S. America spend their entire time in communal roosts, sharing space with 2 other species of martins that don't migrate to N. America. Generally a purple martin will inhabit two or three different roost locations during our fall/winter, often situated hundreds of miles apart.
Current research is advancing rapidly. PMCA, and its collaborators, are at the leading edge of this research. As a result, more is known about the migration of purple martins than any songbird species in the world. Plus, our research is creating a model for capturing and studying other bird species.
You are right: there is a lot about migration that is a mystery, feats of nature beyond our comprehension. We are solving some of those mysteries thanks to membership support.

[Craig Haddox]

Any time between 7am-10am is prime time for arrivals for my colony. I've had a few late arrivals but that 7-10 time frame is the main arrival time here.

[Vern1]

Early in the season, they don't seem to congregate in the sky before they come in to roost.
They wait until right before dark, come into the area at altitude, then zip in very quickly and go straight into a cavity.
They can be very quiet when they come in to roost.
This happens VERY quickly and if you miss that 1-2 minute window, you won't even know they are there.

During the first day or two, they don't seem to be worried about which cavity they will nest in, just look for a place to spend the night.
They seem to rise early, possibly in search of an early breakfast, then congregate on the rack and socialize before they head out for serious foraging.
Again, if you are not watching them, they seem to just appear out of thin air although they might have spent the night before.