Abstract and Citations:
DECADES OF DATA FOR PROTECTED COASTAL RIPARIAN BREEDING BIRD POPULATIONS SHOW PERSISTENT REDUCTION AFTER EXTREME HEAT
David "Doc Quack" Riensche and Christopher L. Kitting
Historical records show that diverse “Canaries in our coal mine” environment generally have
been disappearing, despite protections. Since 1994, we have been conducting periodic,
consistent breeding bird censuses in a protected (since <1973) riparian area on San Francisco
Bay’s east (downwind) shore, relatively stable in local weather and vegetation. Additional,
frequent monitoring detected no changes in predators or dead individuals from disease.
Instead, we detected an overall decline in breeding birds there, hypothetically corresponding to
steadily increasing human activity in adjacent areas. Yet bird declines were not steady at all.
Reports of unusually warm, calm weather around San Francisco Bay in 2004 and 2006
prompted us to compare these old and newer bird data to weather records, which also
illustrated a 2000 heat event locally. To test hypothetical effects of these unusual heat events
of 2000/2004/2006, we compared bird data before and after those years, yielding a clear,
persistent reduction in most breeding avifauna, after those heat events. Annual Maximum
temperatures also became repeatedly >36 degrees C, which might be a threshold for many of
these birds. Such heat again in 2017 did not appear to decrease these bird populations further.
Historical data from 1973 had indicated >34% more territories there, but only minor
subsequent heat through our 1994- data, illustrating previous, additional limits on these birds.
Trends in comparing general weather and breeding bird data might not be clear in such coastal,
relatively benign climates, within birds’ adaptations. Yet occasional, extreme environmental
events, particularly in a protected relatively stable coastal area, appears to have additional
major negative, lasting effects on these breeding populations.
Key Words.—ecology; riparian breeding birds; conservation; climate change, California;
protected wildlife diversity.
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