Data from: Hybridization fluctuates with rainfall in Darwin's tree finches

Hybridization in natural populations may be an adaptive response to
shifting climatic regimes, but understanding this can be limited by
temporal sampling effort and confident hybrid identification. On the
Galapagos Islands, Darwin’s finches regularly hybridize, and the islands
show extreme annual variation in rainfall, however the effect of annual
rainfall on the frequency of finch hybridization is little known. Across a
19-year period on Floreana Island, we compare patterns of hybridization in
sympatric Darwin’s tree finches (N = 425; Camaryhnchus spp.) and test for
an effect of annual rainfall on, 1) the frequency of hybrids (C. pauper ×
C. parvulus), and 2) the percentage of male hybrid birds produced per year
(hybrid recruitment). Annual rainfall correlated with recruitment
positively for hybrids, negatively for C. parvulus and not at all for C.
pauper. Furthermore, the percentage of hybrids (range: 12-56%) and C.
parvulus did not change with sampling year, but the critically endangered
C. pauper declined. Our findings indicate that hybrid recruitment is
recurring and variable according to annual rainfall in Camarhynchus
Darwin’s finches.