[Tweeters] PNS double breeding Rohwer paper online

Kevin Purcell kevinpurcell at pobox.com
Wed Oct 28 16:30:30 PDT 2009

On Oct 28, 2009, at 2:52 PM, Tyler Hicks wrote:

> The discovery of a south bound breeding site seperate from the

> northern breeding site in Neotropical migrants by Rohwer et al. is a

> remarkable find. However, it should be noted that this phenomena has

> been hypothesized for many years in Sedge Wrens in eastern North

> America with much evidence to support it.

Not quite the same phenomena as they start the paper with this
paragraph to make some distinctions:

> Itinerant breeding, wherein the same individuals breed in different

> regions in a single season, is established or suspected for just a

> few species of New and Old World birds (1). Some itinerant breeders

> exploit unpredictable food supplies, so their breeding areas may not

> be in the same place from year to year, as in the red-billed quelea

> (Quelea quelea) (2, 3). However, 2 other species, European quail

> (Coturnix coturnix) and dotterel (Charadrius morinellus), apparently

> breed first in southern regions, then move north with the

> progression of spring to breed again (ref. 4 and Whitfield in ref.

> 5). We suggest that the term migratory double breeding might

> appropriately distinguish species with dual breeding ranges that are

> consistent from year to year. Unlike more nomadic itinerant

> breeders, migratory double breeders move between early and later

> breeding sites that are used reliably from year to year.

The Sedge Wren, I think, falls into the itinerant breeders category
with low site fidelity -- it's an opportunist breeder breeding (as the
paper you cited points out).

The different claim here is that these species (five of them) are
breeding in the north (Neartic) and then migrating to an area known
for birds undergoing "post-breeding molt" (more southerly but still
Neartic) and are breeding there again in one season before moving to
the "final" Neotropical migratory destination. And doing it year after
year. Hence "migratory double breeders".

I think this adds another layer to a previous list discussion of the
proper nomenclature for describing the (apparent) movement of birds
after breeding: post-breeding dispersal versus post-breeding movement
versus migration. If this is true then a whole interesting new
terminology needs to be invented (post-breeding1-pre-breeding2
dispersal) or perhaps we just start to drop the more simplistic ideas
we have :-)
Kevin Purcell
kevinpurcell at pobox.com
twitter: @kevinpurcell

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