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When normal growth rates are suppressed, organisms may undergo a rapid period of increased growth in order to match the physical requirements of a developmental benchmark. This compensatory growth, however, is not without its costs, which can have varying consequences. In nestlings, a major benchmark is that of fledging, which requires advanced physical maturation. In previous studies, compensatory growth and some of its associated costs have been shown in prefledging nestlings but fledging-aged nestlings and the costs they may have sustained needs further study. Here we examine the costs of compensatory growth in late-stage European starling (Sturnus vulgaris) nestlings under the developmental stress of ectoparasitic infestation. Nests were subjected to either the addition of Northern fowl mites (Ornithonyssus sylviarum) or ectoparasite reduction through use of the miticide Permethrin. We followed nestlings throughout development, and at 10 and 20 days of age, assessed structural growth and collected blood to determine hematological measures and corticosterone titers. On day 20, the day prior to when starlings typically leave their natal nest, their brains were harvested. Starlings under ectoparasitic conditions had significantly smaller wingspans, tarsus lengths, and bodyweights on day 10, but on day 20, structural growth was indistinguishable from nestlings in miticide treated nests – suggesting compensatory growth. While we have yet to assess hemoglobin and corticosterone levels, analyses show that brain weight and hematocrit were significantly lower in nests with ectoparasites on day 20, perhaps indicating the protection of necessary physical traits for fledging through compensatory growth at the cost of these less apparent attributes.
Lusk, Elliot, "Creepy Crawly Compensation: Examining the Costs of Ectoparasite-Induced Compensatory Growth in Late-Stage Nestlings" (2021). Biology. 9.