Here are some interesting comments I received from my last post about some of the early migrants I’ve been able to record at night above my house in Maine. You can see the original post here >
Michael O’Brien’s comments:
I’m interested in your assertion that American Robin is strictly a diurnal migrant. Perhaps that is true in some areas, but in Cape May it certainly is not. We regularly see massive American Robin flights at night, in fall at least. These flights often continue or resume in the first few hours of the morning and again in the last hour or so of the day. During particularly heavy flights, the movements may continue longer into the day, but my estimation is that the bulk of the movement always takes place at night. I find their behavior to be much like that of Bobolink, only they seem to be less vocal. It would be interesting to know what others have observed and if the situation is different elsewhere. My guess is that the main difference, if any, is that robins call more frequently in certain situations and fly more quietly in others.
Laura Erickson’s comments:
The BNA for American Robin entry implies that robins do migrate occasionally at nighttime (which is what I learned in ornithology back in the 70s–that they’re like Canada Geese in that they can migrate whenever they darned-well feel like it). BNA says, “Migrating in flocks primarily during the day, birds strike television towers less often than do regular nocturnal migrants,” and “Captive robins kept on a near-normal spring photoperiod of 12:12 to 16:8 h develop migratory restlessness that lasts through both the daytime and nighttime hours (Kemper and Taylor 1981). More information needed.”
When I counted migrating songbirds along Lake Superior during autumns in the 1980s and early 90s, robins were often on the move when we first arrived at or before sunrise.
Of course! Based on the relatively small number of robins killed at towers, everyone’s recording experiences, and other information, it’s clear that robins are not primarily nocturnal migrants. And at least in Duluth, their huge fall movements were always at the tail end of warbler migration–into October while most of the “best” nights for most nocturnal migrants fell in mid-late August and September. It would be fun and interesting to use data from recorders to tease out the conditions that prompt robin nocturnal flights.
Tom Johnson comments:
I’ve heard Common Tern at night once in southeastern Pennsylvania well away from water (so clearly migrating). This was in spring, probably May.
On the robin front, in addition to coastal movements, I’ve heard them in Ithaca while circulating over the lights of the football stadium here several times in the fall, though always greatly outnumbered by Savannah Sparrows, etc.
Michael Lanzone comments:
We do occasionally pick up robins on some of our recordings, but they are few and far between in the night hours (pre 3am) and that is on well over 20k hours of recordings here and in the Appalachians. I tend to hear many more from 3-5am. However, on several occasions here I have observed (visually) on top of Laurel Ridge in PA and Backbone Mtn and Allegheny Front in MD and WV robins during the middle of the night, one time 100s of them flying low in the middle of the night. They were largely silent, I may have heard ~5 calls of 5-600 birds, but may have certainly masked by the high calling rate that night. These birds were forced low because of fog and there was a heavy flight those nights with a lot of flight calling activity, and these spots were lighted and I could readily ID many of the birds coming over with binoculars and naked eye. Almost all of our recording stations are not lit and we purposely do not record in lighted areas as that does inflate call rates, however it would be interesting to compare some of these locations with the darker ones, a study that I had talked about last year, possibly by this fall I can get a few more stations online to do such a comparison. I wonder if robins either call less nocturnally, fly much higher, coastal effects cause a higher calling rate and/or their calls are softer and may be masked by thrushes.