Fledging Success
How many young birds typically fledge?
One measure of a bird's productivity is the number of young it is
able to raise that live long enough to leave the nest (fledgling
stage). This table shows the average number of fledglings per nest
attempt for Western Bluebird, across the United States and Canada,
during the years when participants of The Birdhouse Network have
submitted data (1997-2003).
Looking down the columns at the data for 2003, we find that the average
number of Western Bluebird fledglings varies from region to region:
from 5.3 fledglings in Colorado to only 1.3 in New Mexico.
This could lead us to ask, "what environmental factors in these regions
might contribute to such a difference? Do we see a similar pattern in
other years?" If we do, this might point to long-term environmental
factors such as climate change; if not, this might indicate short-term
factors such as localized weather conditions (colder, hotter, drier,
wetter than usual) affected fledging rates in different regions.