Sex allocation theory predicts that females should bias their offspring sex ratios when the
fitness benefits of producing sons or daughters differ depending on rearing environment …

The invasive avian vampire fly (Philornis downsi, Diptera: Muscidae) is considered one of
the greatest threats to the endemic avifauna of the Galápagos Islands. The fly larvae …

For successful reproduction, timing is important because food availability for birds varies
with time of year and, to ensure sufficient food for both adults and their young, breeding …

In many cooperatively breeding species, helpers increase the breeding success of their
parents. The repayment hypothesis predicts a skewed sex-ratio towards the helping sex at …

Highlights•Population level offspring sex ratio of northern flickers did not differ from
parity.•High-quality parents did not produce more males (the expensive sex).•Flickers …