Does nestbox type significantly alter the ectoparasitic load and breeding success in the nests of secondary-cavity-nesting passerines, at Nagshead, Forest of Dean?

This research aims to find if nestbox type causes a significant difference in the ectoparasite load and breeding success rate in the nests for four co-occurring secondary cavity nesting passerines, breeding in nestboxes at Nagshead Nature Reserve, Forest of Dean. The different nestbox types used in this study are old and new standard wooden nestboxes and deep nestboxes, which are designed to reduced predation. Nests were taken from nestboxes used by Blue Tit (Cyanistes caeruleus), Great Tit (Parus major), Nuthatch (Sitta Europaea) and Pied Flycatcher (Ficedula hypoleuca) by Nestbox Species Surveyors at the end of the 2019 breeding season, and later dissected to determine ectoparasite abundance and nest composition. Nest data collected by Nestbox Species Surveyors was used to calculate the breeding success rate. Population of woodland birds in 2018 was found to be overall 29% than in 1970. Deforestation and habitat management are causes in the reduction of nesting sites available for woodland bird species. Pine Martens (Martes martes), a known predator to secondary cavity nesting birds, were reintroduced into the Forest of Dean in September 2019. Individuals using nestboxes are at a potential increased risk of predation as nestboxes are accessible to Pine Martens. The abundance of adult Hen Fleas and Blowfly pupae in deep nestboxes was found to be significantly higher compared to the nestbox types. Nuthatch nests were found to have the highest mean abundance of adult Hen Fleas, while Pied Flycatcher nests had the highest mean abundance of Blowfly pupae, compared to the other species. Leaves as a nest material were found to have a significant influence and negative correlation with both ectoparasites mentioned. Breeding success rate in standard new boxes was significantly lower than the other nestbox types, with no significant difference occurring between deep and standard old nestboxes. Breeding success in Nuthatch nests were found to be significantly lower than the other avian study species potential linking the increased abundance of adult Hen Fleas previously found. Leaves were found to be significantly influencing and positively correlating with breeding success. These findings add to the data and knowledge about the difference in ectoparasite load and breeding success between nestbox types and the secondary cavity nest passerines, which use these nestboxes. This study also opens up potential for recommended future studies to be carried out at Nagshead.

A parasite reduction conservation intervention does not improve fledging success or most condition metrics for Purple Martins

Eastern Purple Martins (Progne subis subis) have an unusually close relationship with humans, as they nest exclusively in man-made nest boxes. Current conservation policy directly promotes further interaction with this species by advocating regular replacement of nest materials during the nestling phase to reduce ectoparasite load and increase nestling fitness. We conducted the first test of the efficacy of this recommendation and found that it was partially effective in reducing parasite abundance, but had no effect on nestling fledging success, body mass, leukocyte count, or triglyceride or uric acid concentration. We found a small but significant increase in nestling hematocrit associated with nest material replacement, implying that parasites may induce nestling anemia. Contrary to our expectations, we also found elevated heterophil/lymphocyte ratios in nestlings with replacements, possibly indicating elevated physiological stress associated with nest replacements. Based on our results, we do not recommend nest material replacements to combat routine parasite infestations.

Ocean Acidification Does Not Affect Fish Ectoparasite Survival

The juveniles of gnathiid isopods are one of the most common fish ectoparasites in marine habitats and cause deleterious effects on fish by feeding on host blood and lymph. Reef fishes tend to engage in cooperative interactions with cleaning organisms to reduce their ectoparasite load. Ocean acidification (OA) pose multiple threats to marine life. Recently, OA was found to disrupt cleaner fish behaviour in mutualistic cleaning interactions. However, the potential effects of ocean acidification on this common ectoparasite remains unknown. Here, we test if exposure to an acidification scenario predicted by IPCC to the end of the century (RCP 8.5 – 980 μatm pCO2) affects gnathiid survival. Our results show that ocean acidification did not have any effects on gnathiid survival rate during all three juvenile life stages. Thus, we advocate that the need for cleaning interactions will persist in potentially acidified coral reefs. Nevertheless, to better understand gnathiid resilience to ocean acidification, future studies are needed to evaluate ocean acidification impacts on gnathiid reproduction and physiology as well as host-parasite interactions.

Metabolic theory of ecology successfully predicts distinct scaling of ectoparasite load on hosts

The impacts of parasites on hosts and the role that parasites play in ecosystems must be underlain by the load of parasites in individual hosts. To help explain and predict parasite load across a broad range of species, quantitative theory has been developed based on fundamental relationships between organism size, temperature and metabolic rate. Here, we elaborate on an aspect of that ‘scaling theory for parasitism’, and test a previously unexplored prediction, using new data for total ectoparasite load from 263 wild birds of 42 species. We reveal that, despite the expected substantial variation in parasite load among individual hosts, (i) the theory successfully predicts the distinct increase of ectoparasite load with host body size, indicating the importance of geometric scaling constraints on access to host resources, (ii) ectoparasite load appears ultimately limited by access—not to host space—but to host energy, and (iii) there is a currency-dependent shift in taxonomic dominance of parasite load on larger birds. Hence, these results reveal a seemingly new macroecological pattern, underscore the utility of energy flux as a currency for parasitism and highlight the promise of using scaling theory to provide baseline expectations for parasite load for a diversity of host species.

The impact of ectoparasitism on thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Parasites are ubiquitous and can have large impacts on the fitness of their hosts. The effects of ectoparasites on physiology, behaviour, and immune function suggest that they could be part of the factors which impact thermoregulation. We tested the hypothesis that ectoparasites impact thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope in Yarrow, 1875) living along an elevational gradient. We predicted a positive association between ectoparasite load and body temperature (Tb), and a negative association between ectoparasite load and effectiveness of thermoregulation (de – db index). We also predicted that the impacts of ectoparasites would be greatest at high elevation where thermal quality of the environment is low because the costs of thermoregulation increase with elevation and these costs can impact thermal immune responses. We found a significant association between the number of chiggers (Trombiculoidea) harboured by lizards and Tb that depended on elevation, but no association between ectoparasite load and de – db index. The mean chigger infection rate was associated with a ΔTb of +0.18 °C at low elevation (consistent with fever) and of –1.07 °C at high elevation (consistent with hypothermia). These findings suggest that parasitism by chiggers impacts lizard Tb in a way that depends on environmental thermal quality.