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Ian,
 
I have studied Cerulean Warblers in Southern Ohio and West Virginia.  These are considered "hotspots" for the species.  The males down there sang well into July but there territories were really packed-in next to each other.  As Alan was saying I don't believe we ever recorded a double brood for the Cerulean pairs in our study plots. So they could most likely leave earlier than other warbler species.  I love hearing about your interesting finds on Snake Mountain.  Thanks for the insight!
 
Travis Collingwood
 

> Date: Fri, 24 Jun 2011 12:45:17 -0400
> From: [log in to unmask]
> Subject: Re: [VTBIRD] Cerulean couple -- brief Vermont stay?
> To: [log in to unmask]
> 
> The species of long-distance migrants that tend to leave VT earliest in 
> summer are often the ones that have the longest migration distances. 
> Cerulean Warblers winter in northern and central South America (as 
> opposed to the Caribbean and Central America for most of our migratory 
> breeders that leave the US). Bobolinks, Purple Martins, and Upland 
> Sandpipers all winter in South America and most depart VT before the end 
> of summer. The other factor is number of broods/year; birds that raise 
> > 1 brood/year generally migrate later in fall and Cerulean Warblers 
> are generally single brooded. The evolutionary factors behind number of 
> broods per year is not well understood, but is typically thought to be a 
> trade-off between adult survival and birth rates. Thus, given the 
> long-distance migratory strategy, a single brood and mid-summer 
> migration would be predicted to maximize individual fitness.
> 
> Allan
> 
> On 6/24/2011 12:20 PM, Ian Worley wrote:
> > Good question.
> >
> > The apparently brief stay by Ceruleans in the northern parts of their 
> > range is a question I've heard more than once. I'm not a researcher 
> > on the species, but since they inhabit the hill slope behind our 
> > house, I've had the opportunity to follow their activity as best I 
> > can. When few in numbers they are hard to keep track of!
> >
> > Although very little is known about the habits of Ceruleans in 
> > Vermont, I've casually read reports that they are, or are among, the 
> > earliest of warblers in other northernish states to depart from 
> > locations in the northern part of their range - often in July. All 
> > reported observations of the species in Vermont are in only May and 
> > June (May 11th to June 26th) except for one from Grand Isle County in 
> > September 2010 and three reports from Winhall (September of 1984, 
> > 1986, and 1991). If not singing, and if there are few birds anyhow, 
> > they are maddeningly difficult to discover in the forest canopy.
> >
> > On 13 June 2008 Ted Murin and I saw a male carrying food at the 
> > location I reported on earlier today. The first arrivals appear to be 
> > quite consistently between May 11 and 15 here and elsewhere in the state.
> >
> > Last year the birds arrived at my home site May 11th, were noisy and 
> > active till May 23rd, then very subdued until June 4th (a period of 11 
> > days) when activity significantly increased. By June 14th males 
> > started wandering from their previous territories, which are 
> > approximately 700 feet apart. I followed one for over a quarter mile 
> > as it wandered through the woods into terrain farther and farther away 
> > from the May territories. By June 17th it was much harder to find a 
> > bird by sound or sight. The last bird observed was on June 26th, 
> > though I looked systematically daily into mid-July and sporadically 
> > thereafter till October.
> >
> > With those dates in mind, from a May 11th arrival that could give a 
> > couple of weeks to settle territory, mate, and build a nest in May, 
> > with incubation beginning in the last few days of May or even a bit 
> > sooner. Incubation (reported to be 10-12 days) could easily be done 
> > by the end of the first week of June or slightly thereafter. This 
> > corresponds well with the 11 day quiet period mentioned above.
> >
> > Looking forward to other thoughts and knowledge about the apparent 
> > brief residency of these intriguing high canopy dwellers.
> >
> > Ian
> > =============================
> > >>> >>
> 
> -- 
> 
> *******************************************************************
> Allan M. Strong
> University of Vermont
> The Rubenstein School of Environment and Natural Resources
> 007 Hills Building
> Burlington, VT 05405
> 802-656-2910
> *******************************************************************