Griebel IA, Dawson RD (2019) Data from: Experimental reduction of nestling hemoglobin concentration in combination with ectoparasite load manipulation affects nestling morphology and begging behavior, but not adult behavior. Journal of Ornithology https://doi.org/10.1007/ s10336-019-01706-2

Young nest-bound birds often face a diversity of ectoparasites that typically feed on blood and can
negatively affect nestling morphological and physiological traits, including hemoglobin concentration.
While hemoglobin concentration can be correlated with nestling performance, such as body mass, it is
unknown whether variation in hemoglobin is the direct proximate factor responsible for variation in
morphology, or if nestling traits simply co-vary with hemoglobin concentration due to a number of similar
factors influencing both traits. If hemoglobin concentration does directly influence the phenotype of
nestlings, then the reduction in nestling hemoglobin concentration by ectoparasites may cause other
negative effects commonly associated with parasitism. By experimentally reducing the hemoglobin
concentration of nestling Tree Swallows (Tachycineta bicolor) using phenylhydrazine hydrochloride
(PHZ), we tested whether reduced hemoglobin concentration could be the mechanism that causes changes
in nestling morphology and behavior in response to increased parasitism. Parasite loads were manipulated
in conjunction with the PHZ treatment. Nestlings injected with PHZ displayed no change in hemoglobin
concentration 2 days post-injection, whereas control nestlings showed the typical increase that occurs
during early development. By 6 days post-injection, the parasite, but not PHZ, treatment significantly
affected hemoglobin concentration. Both treatments interacted to affect begging intensity, while size and
growth rate of nestlings were only affected by the parasite load manipulation. This study demonstrates the
potential use of PHZ in nestlings to tease apart the effects of parasitism and reduced hemoglobin, but the
results suggest incorporating a second injection of PHZ to better replicate the pattern of hemoglobin
reduction created by hematophagous ectoparasites.