Martín Quiroga

Philornis downsi (Diptera: Muscidae), an avian nest parasite invasive to the Galápagos Islands, in Mainland Ecuador

ABSTRACT Philornis downsi (Dodge and Aitken) is a bird-parasitic muscid fly native to mainland South America that recently invaded the Galápagos Islands where it is parasitizing Darwins finches and other land birds. This parasite was previously known only from Argentina, Brazil, and Trinidad and Tobago. The first report of P. downsi from mainland Ecuador is provided, supporting the hypothesis that the invasion route of P. downsi from its native range to the Galápagos Islands includes mainland Ecuador. Four different morphologies of pupal exuviae, which belong to different fly species, were uncovered. Dipteran puparia were found in 20% of naturally occurring nests collected in 2013 and in 27% of nests in 2014 at the two sites in western Ecuador. P. downsi accounted for 74% and 40% of the puparia in 2013 and 2014, respectively. Two new bird host species for the genus Philornis were recorded: the streak-headed woodcreeper (Lepidocolaptes souleyetii) and the fasciated wren (Campylorhynchus fasciatus). The levels of nest parasitism found were much lower than levels reported for the Galápagos Islands. Finally, parasitism of P. downsi by a parasitoid in the genus Brachymeria (Hymenoptera, Chalcididae) is documented. Overall, 9% of fly puparia collected in 2013, and 19% of those collected in 2014, had parasitoid emergence holes.

LETHAL AND SUBLETHAL EFFECTS OF BOTFLY (PHILORNIS SEGUYI) PARASITISM ON HOUSE WREN NESTLINGS

Abstract. We studied the effect of botfly (Philornis seguyi) parasitism on survival and growth of House Wren (Troglodytes aedon) nestlings. We investigated whether nestling survival was related to (1) the intensity of botfly infestation, (2) age of the nestling at the time it was parasitized, and (3) the order in which a chick hatched within a brood. The prevalence of botfly parasitism was 25%; the mean intensity and age at parasitism were 12.8 larvae per nestling and 3.9 days, respectively. Nestling survival was 42% lower in infested than in noninfested broods. Nestling survival was negatively associated with the mean intensity of parasitism of the brood and positively associated with the age of the nestling at the time it was parasitized. Within infested broods, nestling survival was higher in chicks hatched first than in chicks hatched last. Infested nestlings that survived until fledging grew at lower rates and remained in the nest longer than did nestlings in noninfested broods. Our results reveal that P. seguyi has lethal and sublethal effects on House Wren nestlings and that the intensity of parasitism, age of nestlings at the time they are infested, and sequence of hatching are important factors that influence the survival of parasitized nestlings.

Sequence analysis of the internal transcribed spacer 2 (ITS2) from Philornis seguyi (García, 1952) and Philornis torquans (Nielsen, 1913) (Diptera: Muscidae)

Philornis Meinert, 1890 (Diptera: Muscidae) is a genus of Neotropical dipterans that parasitise birds. The currently used external morphological characters to distinguish between species within this genus present some limitations. We used the second internal transcribed spacer region (ITS2) of the rRNA gene as a molecular marker to differentiate adult specimens of Philornis identified morphologically as Philornis torquans and Philornis seguyi from different localities. Specimens identified as P. seguyi from Magdalena (Buenos Aires Province) showed an ITS2 sequence different from that for P. torquans, whereas all other specimens of P. seguyi had sequences identical to those for P. torquans. These findings do not necessarily confirm that specimens from Magdalena indeed belong to P. seguyi, nor that P. seguyi is a valid species. Instead, they alert us about the potential for species misidentification when using morphological characters alone. The use of molecular approaches to aid the identification of Philornis spp. will shed light on the systematics of this group. P. torquans is reported for the first time in Mendoza Province and Uruguay.

Sexual Differences in Life History Traits of Philornis seguyi (Diptera: Muscidae) Parasitizing House Wrens (Troglodytes aedon)

ABSTRACT We studied life history traits of Philornis seguyi García, 1952 (Diptera: Muscidae) parasitizing house wrens, Troglodytes aedon (Vieillot) (Passeriformes: Troglodytidae), and analyzed sexual differences in the size of larvae, pupae, and adults, as well as in the length of larval and pupal stages and in adult survival. Males were larger than females at the larval, pupal, and adult stages, but there were no sexual differences in the length of larval and pupal stages, or in the time adults survived. Larvae developed in 5–6 d and started the larval-pupal molt within 24 h after abandoning the host. Pupal stage lasted for 9 d and its length was positively associated with size of the pupa. The size of the pupa was positively associated with that of the larva and the size of the adult with that of the pupa. In laboratory conditions, 86% of the larvae pupated and 75% of the pupae emerged as adults. In natural conditions, the proportion of unsuccessful pupae increased by the end of hosts breeding season. The proportion of males and females that survived until the adult stage did not differ from random. Our results show that P. seguyi has a relatively short generation time, which would allow it a rapid population growth during the host breeding season, and indicate that intrasexual selection may have selected for large body size in P. seguyi males.

Contrasting consequences of different defence strategies in a natural multihost–parasite system

Hosts counteract infections using two distinct defence strategies, resistance (reduction in pathogen fitness) and tolerance (limitation of infection damage). These strategies have been minimally investigated in multi-host systems, where they may vary across host species, entailing consequences both for hosts (virulence) and parasites (transmission). Comprehending the interplay among resistance, tolerance, virulence and parasite success is highly relevant for our understanding of the ecology and evolution of infectious and parasitic diseases. Our work investigated the interaction between an insect parasite and its most common bird host species, focusing on two relevant questions: (i) are defence strategies different between main and alternative hosts and, (ii) what are the consequences (virulence and parasite success) of different defence strategies? We conducted a matched field experiment and longitudinal studies at the host and the parasite levels under natural conditions, using a system comprising Philornis torquans flies and three bird hosts - the main host and two of the most frequently used alternative hosts. We found that main and alternative hosts have contrasting defence strategies, which gave rise in turn to contrasting virulence and parasite success. In the main bird host, minor loss of fitness, no detectable immune response, and high parasite success suggest a strategy of high tolerance and negligible resistance. Alternative hosts, on the contrary, resisted by mounting inflammatory responses, although with very different efficiency, which resulted in highly dissimilar parasite success and virulence. These results show clearly distinct defence strategies between main and alternative hosts in a natural multi-host system. They also highlight the importance of defence strategies in determining virulence and infection dynamics, and hint that defence efficiency is a crucial intervening element in these processes.

Song structure of the golden-billed saltator (Saltator aurantiirostris) in the middle Parana river floodplain

Bird communication is a growing field of study in ethology and evolutionary biology; however, most known studies were conducted only in the northern hemisphere. We measured six temporal and structural features of golden-billed saltator (Saltator aurantiirostris) song and recorded 57 vocalizations at Parque San Martín reserve (Argentina). Results indicated that the prelude represented between two and four syllables, while the trill was composed of one to three. The complete song always contained six syllables. Maximum and minimum frequencies were higher in the trill. The duration of prelude and trill did not differ between vocalizations. Modifications and differences observed in vocalizations may be explained by the acoustic adaptation hypothesis, which predicts higher frequencies in open habitats. Our results broaden and supplement the data available for this species in Argentina, representing useful information for studies intended to assess the effect of different habitats on birds vocalizations in southern South America.

Diet of Cattle Egrets ( Bubulcus ibis ibis ) in the flood valley of the Paraná River, northern Argentina

We analysed the feeding ecology of Cattle Egrets (Bubulcus ibis ibis) based on 30 individuals captured on the Carabajal island, Santa Fe, Argentina (31°39′S, 60°42′W), determining the minimum sample, index of relative importance (IRI), size of prey, feeding efficiency, dietary selectivity, amplitude of the trophic niche, standardisation, circadian rhythm of feeding activity and habitat preference. The trophic spectrum was made up of 17 taxonomic entities, mainly insects (IRI = 15,000), among which orthopterans were the most numerous followed by spiders and amphibians (IRI = 250). The highest percentage of prey size was found in the interval 21-30 mm. The amplitude of the trophic niche ranged between 1.98 and 3.45, and the feeding efficiency between 89 and 92%. In relation to dietary selectivity, the correlation between abundance of prey in stomachs and abundance of prey in the study area yielded no significant results (rs = 0.84, P.0:001). The rhythm of feeding activity responded to the bell-shaped model, which meant a peak in its feeding behaviour pattern at the noon hours. The pastures were the units of vegetation and environment selected more frequently.

The tropical fowl mite, Ornithonyssus bursa (Acari: Macronyssidae): environmental and host factors associated with its occurrence in Argentine passerine communities

The tropical fowl mite, Ornithonyssus bursa, is a common avian parasite found on diverse bird species worldwide. In the Neotropical region, O. bursa is present in wild birds, but it may also infect poultry and bite humans. Little is known about the ecology and epidemiology of this parasite. We conducted a thorough longitudinal study in passerine assemblages from central Argentina, gathering data from six reproductive seasons, with the aim of identifying factors that have a role in driving the occurrence and distribution of O. bursa in its natural hosts. We focused on the brood and microhabitat levels, accounting for potential confounders of higher levels. The results hereby presented contribute to our knowledge on the eco-epidemiology of O. bursa in natural hosts of the Neotropical region. Among the many variables assessed, nest material and host species appeared to be the most important correlates of O. bursa prevalence. Nonetheless, supplementary analyses showed that host species is a stronger predictor than nest material. Moreover, mite burden (parasite intensity) was found to depend on host species, but not on nest material. The association with species depended on nestling age, suggesting that resistance builds up as the nestling develop, but at a different pace depending on the bird species. Brood size was inversely correlated with intensity of parasitism, suggesting a dilution of the parasite burden on each nestling.