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Here is a link to a PDF file that shows the year-by-year banding results by species since 2004.
Of interest, over the years, the Rio Grande Research team newly banded a total of 2476 rosy-finches to date. Of these, 54.28% were Black Rosy-Finches. The Brown-capped species accounted for 27.46% of all newly banded, while Gray-crowned made up 18.26%.
Over the years the numbers and percentages of each species have gyrated widely. The percentage of Black Rosy-Finches has ranged from 15% (in 2007-08) to 77% in 2010-11. Brown-capped Rosy-finch percentages varied from 1% in 2006-07 to 63% the next season! Gray-crowned species made up a high of 25% of the newly banded, in 2006-07 down to only 3% in 2011-12 and none at all last season (2013-14). In addition to the newly banded birds, a large number of recaptures are not reflected in these statistics.
What accounted for these fluctuations in abundance of the various species, and also of the Hepburn's subspecies of the Gray-crowned? The latter have been particularly abundant some seasons and rare to absent in others. Is there some relationship to regional weather patterns in their home ranges as well as at Sandia Crest? Do the changes represent variations in total populations of each taxa, or changes in migration patterns? The absolute number of Black Rosy-Finches banded shows an irregular but definite downward trend since 2006-07. Is this statistically significant? Might it reflect differences in the number of banding sessions in different years? Food for thought and research.
Thanks to Nancy Cox for providing these updated statistics.
Rosy-Finch Banded Numbers By Year (PDF):
http://www.rosyfinch.com/RosyFinchBandedNumbersByYear.pdf
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