Nest parasitism, promiscuity, and relatedness among wood ducks

Nest parasitism is a common reproductive strategy used by many species of cavity nesting birds. Among these, the wood duck (Aix sponsa) is known to have evolved very specific strategies of when and whom to parasitize that is often based on population and/or environmental queues. Here, we investigated the genetic relationship of two female wood ducks competing over an artificial nesting box in Delaware, including the continued incubation of one female despite the death and body remains of the other female throughout the incubation process. We test whether such an extreme case of nest parasitism can be explained by relatedness, egg lineage composition, or a combination of other factors. To do so, we extracted genomic DNA from blood and tissue of the females, as well as chorioallantoic membranes of all viable and inviable eggs. Subsequently, we assessed relatedness among females and eggs based on hundreds of nuclear loci and the mitochondrial control region. We concluded that (1) the two incubating females were entirely unrelated, (2) the single clutch is in fact represented by a minimum of four unrelated females, and (3) a single female can lay eggs sired by different males. The latter finding is the first direct evidence for successful extra-pair copulation in wood ducks. With decreasing costs and increasing effectiveness, genomic methods have the potential to provide important insights into more complex ecological and evolutionary tactics of such populations.

Differential effects of elevated nest temperature and parasitism on the gut microbiota of wild avian hosts

Background Changes in wild animal gut microbiotas may influence host health and fitness. While many studies have shown correlations between gut microbiota structure and external factors, few studies demonstrate causal links between environmental variables and microbiota shifts. Here, we use a fully factorial experiment to test the effects of elevated ambient temperature and natural nest parasitism by nest flies (Protocalliphora sialia) on the gut microbiotas of two species of wild birds, the eastern bluebird (Sialia sialis) and the tree swallow (Tachycineta bicolor). Results We find that bacterial communities from the nestlings of each host species show idiosyncratic responses to both heat and parasitism, with gut microbiotas of eastern bluebirds more disrupted by heat and parasitism than those of tree swallows. Thus, we find that eastern bluebirds are unable to maintain stable associations with their gut bacteria in the face of both elevated temperature and parasitism. In contrast, tree swallow gut microbiotas are not significantly impacted by either heat or nest parasitism. Conclusions Our results suggest that excess heat (e.g., as a result of climate change) may destabilize natural host-parasite-microbiota systems, with the potential to affect host fitness and survival in the Anthropocene.

Owens Valley nesting willow flycatcher under pressure

Willow flycatchers (Empidonax traillii; WIFL) nest along the Owens River and Horton Creek in the Owens Valley. Migrating WIFL visit these sites as well as many other tributaries to both the Owens River and Mono Lake. We estimate there are approximately 35 WIFL territories in the Owens valley, or 5% of territories in California. Nesting WIFL in the Owens Valley are likely the federally endangered southwestern subspecies (E. t. extimus; SWIFL). The Chalk Bluff nesting site is particularly important as large nesting areas tend to be both rare and important for SWIFL and it contains more than half (63%) of all known WIFL territories in the region, which also represents 12% of all nesting SWIFL in California. Between 2014 and 2016, WIFL territory numbers declined from 37 to 27 across the three largest breeding sites. Territory numbers may have been influenced by drought conditions or brown-headed cowbird (Molothrus ater; BHCO) nest parasitism. In 2015 and 2016, comprehensive nest monitoring found nest parasitism rates were >40%, and nest success was lower in parasitized nests (16%; N = 5/31) compared with non-parasitized nests (60%; N = 31/52). BHCO management could potentially improve nest success for WIFL as well as many other open-cup nesting riparian birds in the Owens Valley.

The morphometric analysis of Eurasian coot eggs (Fulica atra) under the local conditions from Câmpenești, North-Western Romania

The aim of the present paper was to analyze the measurements of the Eurasian Coot (Fulica atra) eggs in order to evaluate if the local conditions, presented here, differ in some way from older data found in references dating to 1955 in Romania. The data were collected from the Eurasian Coot nests identified (N=8) at Câmpenești fishponds, located in North-Western Romania, in May 2018. The clutch size was 7.5 ±1.6, ranging from 5 to 10 eggs. The mean egg length was 50.81 mm, and the mean egg breadth was 34.5 mm with higher variability in case of the first measurement. The mean egg volume was 31.3 cm3 which is much smaller than reported in the Romanian references (36.13 cm3). Regarding intra-clutch variance, we found that some clutches manifest a higher length, breadth and volume variance than others which can be a result of the intraspecific nest parasitism or environmental variances. The results brought some extensions of egg length and egg breadth limits and also may reflect a decrease in egg size over time.

[Red-crested pochard, Netta rufina, breeding population in Piedmont (North Western Italy)]

[The breeding of the Red-crested pochard in Piedmont is known since 2006, when it was first described in a pond near the town of Asti. Data were collected from specific databases and from field observations performed in 3 sites located in the Asti province and 2 sites in the Cuneo province, all of them placed along the Tanaro riversides. A further site is located in the province of Alessandria near the Po river along the border of Lombardy. On the whole, in the time span 2006-2019 the number of breeding pairs increased from 2 to a maximum of 7 per year. A total of 64 females with 326 chicks were recorded (average 5.1/female), June being the most favorable month for reproduction. Results point to the occurrence of a seemingly stable small breeding population. The lack of any kind of legal site protection, the anthropogenic disturbance (hunting, fishing, abandoning wastes), and the loss of the ideal habitat for reproduction are among the critical threats for the maintenance of a vital breeding population. There was a probable case of nest parasitism by Mallard duck, which is seldom observed since the opposite situation seems to be more common.] [Article in Italian]

New species on the list of species with intraspecific nest parasitism

Intraspecific nest parasitism has only recently received more attention from ornithologists. In 2001, Yom-Tov published a list of 234 species that had exhibited this behaviour. I have since found literature data on four additional species in which intraspecific nest parasitism has been observed. No such record has so far been published from Hungary. This study presents records on 25 species from Hungary and on one species from Croatia, out of which I have not found any reference for intraspecific nest parasitism in the literature for Cattle Egret (Bubulcus ibis), Eurasian Thick-knee (Burhinus oedicnemus), Black-winged Stilt (Himantopus himantopus), Collared Pratincole (Glareola pratincola), Mediterranean Gull (Larus melanocephalus), Little Tern (Sternula albifrons), Whiskered Tern (Chlidonias hybrida), Eurasian Roller (Coracias garrulus) and Eurasian Jackdaw (Corvus monedula). In addition to records from Hungary, for Black-headed Gull (Larus ridibundus) and Mediterranean Gull I also present observations from Slovakia, and for Common Shelduck (Tadorna tadorna) from Germany.

Additive negative effects of Philornis nest parasitism on small and declining Neotropical bird populations

SummaryThe declining-population paradigm holds that small populations are particularly vulnerable to anthropogenic influences such as habitat destruction, pollution and species introductions. While the effects of particular stressors, such as parasitism, may be unimportant in a large, healthy population, they can be serious and even devastating in situations characterised by a restricted geographic range, or by fragmented or reduced population sizes. We apply this idea to nest parasitism of threatened Neotropical bird species that exist in small populations, focusing on dipteran nest parasites in the genusPhilornis. We review the literature onPhilornisparasitism exerting negative pressure on bird populations that have become small and isolated due to human actions and present a new case ofPhilornisparasitism of a threatened hummingbird species. Our aim is to raise awareness about the exacerbating effect that nest parasites can have on small and declining bird populations; especially when biological information is scarce. The five reviewed cases involve two species of Darwin’s Finches in the Galápagos Islands attacked by the invasiveP. downsi, two species of hawks on islands in the Caribbean attacked by the nativeP. piciandP. obscura, and the Yellow CardinalGubernatrix cristatain southern South America attacked by an unknownPhilornisspecies. We also present new documentation of parasitism of a threatened hummingbird species in mainland Ecuador by an unidentifiedPhilornisspecies. We recommend more field studies to determine the presence of nest parasites in bird populations worldwide to improve understanding how nest parasites affect bird fitness and population viability and to allow time to act in advance if needed. Parasitism byPhilornismay represent a severe mortality factor in most already threatened bird species, putting them at greater risk of extinction. Therefore, parasitism management should be included in all threatened species recovery plans.

Intra- and interspecific nest parasitism of Common Moorhen (review of cases and new data)

Based on data available so far, it seems that Common Moorhens (Gallinula chloropus) rarely, but regularly lay one or more eggs in the nests of Common Little Bittern (Ixobrychus minutus). Three such incidents from Hungary are hereby added to the cases known to date. However, Common Moorhens do not only lay eggs in other species’ nests, but also in the nests of conspecifics, while other species may also parasitise the nest of Common Moorhens. The present study summarises these aspects.