Haematophagous ectoparasites lower survival of and have detrimental physiological effects on golden eagle nestlings

Abstract

Haematophagous ectoparasites can directly affect the health of young animals by depleting blood volume and reducing energetic resources available for growth and development. Less is known about the effects of ectoparasitism on stress physiology (i.e. glucocorticoid hormones) or animal behaviour. Mexican chicken bugs (Haematosiphon inodorus; Hemiptera: Cimicidae) are blood-sucking ectoparasites that live in nesting material or nest substrate and feed on nestling birds. Over the past 50 years, the range of H. inodorus has expanded, suggesting that new hosts or populations may be vulnerable. We studied the physiological and behavioural effects of H. inodorus on golden eagle (Aquila chrysaetos) nestlings in southwestern Idaho. We estimated the level of H. inodorus infestation at each nest and measured nestling mass, haematocrit, corticosterone concentrations, telomere lengths and recorded early fledging and mortality events. At nests with the highest levels of infestation, nestlings had significantly lower mass and haematocrit. In addition, highly parasitized nestlings had corticosterone concentrations twice as high on average (42.9 ng/ml) than non-parasitized nestlings (20.2 ng/ml). Telomeres of highly parasitized female nestlings significantly shortened as eagles aged, but we found no effect of parasitism on the telomeres of male nestlings. Finally, in nests with higher infestation levels, eagle nestlings were 20 times more likely to die, often because they left the nest before they could fly. These results suggest that H. inodorus may limit local golden eagle populations by decreasing productivity. For eagles that survived infestation, chronically elevated glucocorticoids and shortened telomeres may adversely affect cognitive function or survival in this otherwise long-lived species. Emerging threats from ectoparasites should be an important management consideration for protected species, like golden eagles.

Corticosterone release in very young siblicidal seabird chicks (Rissa tridactyla) is sensitive to environmental variability and responds rapidly and robustly to external challenges

“…Finally, other aspects of interannual environmental variability could modulate the relationship between food availability and corticosterone by imposing additional energetic challenges. For example, weather can affect chick corticosterone (Crino et al, 2020; De Bruijn and Romero, 2018), as can ectoparasites (Dudek et al, 2021; Kitaysky, 2001; Quillfeldt et al, 2004).…”

Ectoparasitism and Energy Infrastructure Limit Survival of Preadult Golden Eagles in the Southern Great Plains

“…We note, however, that juvenile eagles we studied were not selected randomly from nesting territories across the SGP, and thus we cannot report or speculate about distribution of MCB parasitism across the region. Parasitism of nestling Golden Eagles by MCBs has been documented across a relatively small part of the eagles' range elsewhere in North America: Chihuahua, Mexico (Morales-Yañez and Rodríguez-Estrella 2019), Arizona (K. Jacobsen, Arizona Game and Fish Department, unpubl data), and Idaho (McFadzen et al 1996, Dudek 2021). The range of MCBs may be increasing, however, in response to increasing temperatures under a changing global climate regime (Dudek 2017).…”

“…Now, MCBs frequently occur in Golden Eagle nests in the area especially at nests with southerly exposures and at nests of pairs that breed late in the season, indicating a link between incidence of MCB parasitism and warmer temperatures (Dudek 2017). Hematophagy by MCBs affects nestling Golden Eagles by reducing hematocrit levels and mass, and increasing corticosterone levels (Dudek 2021). Nestlings either fledge prematurely or die in the nest as we noted, although our observations imply they also may die after fledging.…”

“…When we entered some Golden Eagles' nests in the SGP, we found late nestlings that had died within ∼3 d. We collected such birds for formal necropsy as described above unless their remains were badly decomposed due mainly to ambient temperatures exceeding 32°C. During 2017 we found that many late nestlings in the SGP were heavily parasitized by Mexican chicken bugs ( Haematosiphon inodorus ; MCBs), a haematophagous member of the Cimicidae (Hemiptera; Lee 1954, Dudek 2021). We attached PTTs to the affected nestlings if they did not appear weak and had normal mass (≥2800 g and ≥3800 g for males and females, respectively; sex subsequently confirmed by DNA analysis [Animal Genetics, Tallahassee, FL, USA]).…”

Predator-Proofing Avian Nestboxes: A Review of Interventions, Opportunities, and Challenges

“…), likely due to the increased nest volume. The effects of parasitism can manifest either during the nesting period as anaemia and slow growth for chicks and weight loss for adults [106][107][108][109], or afterwards via carry-over effects [110,111]. The positive relationship between nest volume and ectoparasite load in deep boxes might be offset to an extent by the larger distance between nest cup and entrance hole, as this decreases parasitism by blowfly since the nest is harder for free-living adults to detect [92].…”