TY - JOUR
T1 - Philornis downsi parasitism is the primary cause of nestling mortality in the critically endangered Darwin's medium tree finch (Camarhynchus pauper)
AU - O'Connor, Jody
AU - Sulloway, Frank
AU - Robertson, Graham
AU - Kleindorfer, Sonia
PY - 2010/2
Y1 - 2010/2
N2 - Darwin's medium tree finch (Camarhynchus pauper) meets the 2009 International Union for Conservation of Nature Red List criteria for a critically endangered species because it has "a very small range on a single island" and is "declining rapidly owing to the effects of the parasite Philornis downsi", habitat degradation, and introduced predators. The medium tree finch is only found in patches of remnant highland forest on Floreana Island, where it co-exists with breeding populations of small and large tree finches (C. parvulus and C. psittacula). Here, we examine the intensity of P. downsi in nests of small, medium, and large tree finches on Floreana. We expected that parasite intensity would increase with finch body size, and with greater rainfall, and would also correlate with increased nestling mortality. We found a trend in the expected direction for parasite intensity and rainfall. Combined meta-analytically with data from a previous study, the overall trend for the two studies was significant. We also found a significant linear trend in parasite intensity with finch body size. In addition, the medium tree finch exhibited a somewhat higher parasite intensity than would be expected based on body mass alone. Of 63 active medium tree finch nests, 17 nests had nestlings: all of which were infested with P. downsi. Only 25% of medium tree finch nestlings fledged, 28% were depredated, 41% died due to P. downsi parasitism, and 6% died for other reasons.
AB - Darwin's medium tree finch (Camarhynchus pauper) meets the 2009 International Union for Conservation of Nature Red List criteria for a critically endangered species because it has "a very small range on a single island" and is "declining rapidly owing to the effects of the parasite Philornis downsi", habitat degradation, and introduced predators. The medium tree finch is only found in patches of remnant highland forest on Floreana Island, where it co-exists with breeding populations of small and large tree finches (C. parvulus and C. psittacula). Here, we examine the intensity of P. downsi in nests of small, medium, and large tree finches on Floreana. We expected that parasite intensity would increase with finch body size, and with greater rainfall, and would also correlate with increased nestling mortality. We found a trend in the expected direction for parasite intensity and rainfall. Combined meta-analytically with data from a previous study, the overall trend for the two studies was significant. We also found a significant linear trend in parasite intensity with finch body size. In addition, the medium tree finch exhibited a somewhat higher parasite intensity than would be expected based on body mass alone. Of 63 active medium tree finch nests, 17 nests had nestlings: all of which were infested with P. downsi. Only 25% of medium tree finch nestlings fledged, 28% were depredated, 41% died due to P. downsi parasitism, and 6% died for other reasons.
KW - Bird
KW - Body size
KW - Fledging success
KW - Galápagos Islands
KW - Introduced species
KW - Larvae
KW - Mortality
KW - Parasite
UR - http://www.scopus.com/inward/record.url?scp=76449112761&partnerID=8YFLogxK
U2 - 10.1007/s10531-009-9740-1
DO - 10.1007/s10531-009-9740-1
M3 - Article
VL - 19
SP - 853
EP - 866
JO - Biodiversity and Conservation
JF - Biodiversity and Conservation
SN - 0960-3115
IS - 3
ER -