Question: Yellow Warbler - arrivals vs transients

Yellow Warbler: As a general impression, the local males show up on their summer territories before we start to detect many at the migrant traps along the lake. Is this an illusion, or does it reflect the actual pattern of their migration? Photo by Kenn Kaufman.

April 26 (Audubon's birthday): Here in the region of the Lake Erie shoreline, the woodlots or "migrant traps" along the immediate lake shore have such a concentrating effect that we usually detect migrants there before we start to see them elsewhere in the vicinity.  An exception to this pattern involves Yellow Warbler, which is one of the few warblers to nest commonly in this area.  My impression from past years -- borne out by observations the last few days -- is that male Yellow Warblers show up on their nesting territories a mile or two south of the lake first.  Today they were singing vigorously in several spots south of the Magee boardwalk, such as near BSBO and the Sportsmen's Center, but the first migrants are just now showing up at the boardwalk itself.

Does this mean that the birds that are going to nest here arrive first, while the transients going farther north arrive later?  Or are the local summer resident birds just a lot more conspicuous because they are singing and setting up territories? 

Incidentally, something like this happens with Willow Flycatcher later in the spring.  In the latter part of May, they suddenly show up on their territories in the scrub-shrub habitat around BSBO, and only a few days later they start to become conspicuous in the migrant traps right on the lake shore.  But again, the singing, territorial males are a lot easier to detect than the transient individuals.

So for the moment I have a question without a solid answer.  I suspect that local breeders are among the very first Yellow Warblers to reach this latitude, but I don't know that for sure, and I'll have to look into it further.