birding-aus

US songbirds getting smaller, possibly as a result of climate change

To: Ian May <>
Subject: US songbirds getting smaller, possibly as a result of climate change
From: Laurie Knight <>
Date: Sat, 13 Mar 2010 18:52:16 +1000
If you have measured more than 486,203 birds over a period of several decades, then you might be in a position to throw stones, Ian.




Declining body sizes in North American birds associated with climate
change
Josh Van Buskirk 1 , Robert S. Mulvihill 2 and Robert C. Leberman 2
1 Inst. of Zoology, Univ. of Zürich, CH-8057 Zürich, Switzerland, and:
Dept of Zoology, Univ. of Melbourne, 3010 Victoria, Australia 2
Powdermill Avian Research Center, Carnegie Museum of Natural History, Rector, PA 15677-9605, USA
Oikos Early View   Published Online: 2 Mar 2010  DIGITAL OBJECT
IDENTIFIER (DOI) 10.1111/j.1600-0706.2009.18349.x
Recent climate change has caused comparatively rapid shifts in the
phenology and geographic distributions of many plants and animals.
However, there is debate over the degree to which populations can meet the challenges of climate change with evolutionary or phenotypic
responses in life history and morphology. We report that migrating
birds captured at a banding station in western Pennsylvania, USA, have exhibited steadily decreasing fat-free mass and wing chord since 1961, consistent with a response to a warmer climate. This confirms that
phenotypic responses to climate change are currently underway in
entire avian assemblages. Declines in body size were not explained by an index of habitat condition within the breeding or wintering
distributions. Instead, size was negatively correlated with
temperature in the previous year, and long-term trends were associated with the direction of natural selection acting on size over the winter: species undergoing the strongest selection favoring small wing chord showed the most rapid long-term declines in wing. Phenotypic
changes are therefore in line with the prevailing selection regime.

Paper manuscript accepted 12 November 2009




On 13/03/2010, at 6:28 PM, Ian May wrote:

C'mon Laurie!   It's not April 1 yet.   Didn't we read last year
that birds forced up the mountains by higher temperatures are
becoming smaller too.  If this keeps going, crows will be smaller
than blow flies.

Are these climate change findings an example of robust peer reviewed science or just quotes from grey literature?


Regards


Ian

Laurie Knight wrote:

http://news.bbc.co.uk/earth/hi/earth_news/newsid_8560000/8560694.stm

Climate linked to smaller birds
By Matt Walker

Editor, Earth News

Songbirds in the US are getting smaller, and climate change is
suspected as the cause.

A study of almost half a million birds, belonging to over 100
species,  shows that many are gradually becoming lighter and
growing shorter  wings.

This shrinkage has occurred within just half a century, with the
birds  thought to be evolving into a smaller size in response to
warmer  temperatures.



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