Date: 5/2/18 5:35 am From: Bill Volkert <billvolkert11...> Subject: [wisb] Spring Migration Rush
The quick turn of the weather has not only kicked the migration into high gear in southern Wisconsin, but as often happens with these kinds of weather events is that things arrived somewhat out of order. When the birds are held back in spring, due to cold weather and north winds, and the migration stalls for a while and this is followed by strong south winds it not only allows some of the species that have been held back to finally arrive, but these kinds of events can also result in other species arriving a bit earlier than normal and mixing up the sequence of a normal spring migration.
I usually think of warblers arriving in the following order over a period from mid-April to the middle of May: Yellow-rumps always precede others by 2 to 3 weeks, followed by Palm warbler, then... Yellow warbler, black-throated green and black-and-white Blackburnian, Nashville, chestnut-sided, American redstart Parula, Tennessee, magnolia, Cape May, golden-winged warbler, etc.
I am sure that others might modify this list somewhat, but in general there is a progression to when the different species arrive. This year the yellow-rumps were very sparse and I think there was significant mortality among those that arrived before the spring snowstorm hit. However, with the increase of yellow-rumps yesterday, including more males, it seems that some of them were held back and only arrived on the recent south winds.
I also had one blackburnian, a Cape May and one or two Nashville warblers, but no yellow warblers so far. The palm warblers also just arrived and I have had only two sightings of black-and-white warbler and no black-throated greens. Of course, this is only from what I have seen in my neighborhood, but I tend to get a good representation of songbirds in spring so this tends to be a reflection of what is going on in the northern Kettle Moraine.
I also had several Swainson's thrushes in my woods but other species were not present. With south winds last night and some other warm fronts still to come things will get back on track, but I have often noticed this kind of event that when birds are making up for lost time in spring they don't always arrive in the same order as I would expect them - some finally arrive that were held back, others are yet to come, and some species arrive earlier than expected as they take advantage of strong winds.
I also have mentioned this several times in the past, but I am always interested how quick you have to be on your bird song recall in spring after not hearing bird songs for so many months. When the birds first arrive it is common to hear them sing only once or twice which may get your attention, but if it isn't a complete song or is heard at a distance it is sometimes difficult to confirm a new arrival if it doesn't sing a second time or produce a more complete song.
It seems to me that newly arrived birds will often sing very briefly, if at all, on the first day they are here. I would assume that a common explanation is that they are just too tired to sing. While this is somewhat accurate I would think that they are so intent on refueling and finding food after a long flight that singing isn't a priority. I usually find that the next morning after birds have arrived they will sing much more actively and a species that I think I may have briefly heard on the previous day is now easily confirmed as a new arrival.
Spring migration is always interesting to me as the season unfolds and as we see the normal sequence of events progress, as well as years where there is variation from the normal trend.