I learned a new term from the paper in the next post, below this one, and wanted to explore it a little more. The term is "hand-wind index" or "HWI." The HWI measurement can be used for anything from predicting avian egg shape to fledgling dispersal distance and migration.
Quote below from (also see next post): Avian egg shape: Form, function, and evolution -
http://science.sciencemag.org/content/356/6344/1249.full"We also used biometric measurements from museum specimens to calculate the hand-wing index (HWI), a standard proxy for flight efficiency and dispersal ability in birds (13, 28, 29). We computed HWI as the ratio of Kipp's distance (the distance between the tip of the longest primary and the tip of the first secondary feather) to total wing chord (distance between the carpal joint and wingtip) (29). Although HWI correlates with dispersal distance and migratory behavior in birds (13), we note that neither dispersal distance nor migration completely captures the essence of flight ability, because many bird species (e.g., some shorebirds and hummingbirds) fly well even though they are nonmigratory with low dispersal. Using HWI as an index of flight ability sidesteps this issue because even resident species with stronger and more frequent flight tend to have narrower and more pointed wingtips (high HWI), whereas species with weaker and less frequent flight tend to have shorter, more rounded wingtips (low HWI) (13)."
Linear measurements used to calculate the hand-wing index: (WL) 'wing length' from the carpal joint to the tip of the longest primary feather; (SL) 'secondary length' from the carpal joint to the tip of the first secondary feather. Both measurements were taken on closed wings without flattening their natural curvature. Here, WL and SL are traced on a wing outline of Xenops rutilans (University of Washington Burke Museum 77 384) to show their relationship with the extent and width of the wing.
Empirical evidence supports the hand-wing index as a valid surrogate for flight and dispersal ability in birds. Flight performance (see the electronic supplementary material), migratory behaviour [29,30], natal dispersal distance [31] and genetic differentiation [32] are all correlated with this index. Because the index varies on a continuous scale, it can be used to study higher order relationships between dispersal and diversification like the intermediate dispersal model.
Above from: High dispersal ability inhibits speciation in a continental radiation of passerine birds:
http://rspb.royalsocietypublishing.org/content/279/1733/1567?ijkey=b24df22f08aeaa3348a938e375fa003e4a588fad&keytype2=tf_ipsecshaQuote below from: Ecomorphological predictors of natal dispersal distances in birds:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2008.01504.x/abstract;jsessionid=67E55A563A03BD0175A8DC005ED2E55C.f04t03"A multipredictor model that includes Kipp's distance (a measure of wing tip length), bill depth and tail graduation explains 45% of the interspecific variation in natal dispersal distance. These morphological characters all relate to aerodynamics with stronger flyers dispersing further.
However, an index of migration is a strong (but less informative) correlate of dispersal distance and Kipp's distance and bill depth are strong correlates of migration. Thus, we cannot disentangle whether these ecomorphological traits influence dispersal distance directly or whether the relationship between ecomorphology and dispersal is mediated through migratory behaviour.
Notwithstanding uncertainties regarding the causal links between dispersal distance and wing morphology, we suggest that two ecomorphological traits, Kipp's distance and bill depth, may provide a useful surrogate."
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Topic: New developments in the field of science (Read 447746 times)