Review of the biology and host associations of the wasp genus Gasteruption (Evanioidea: Gasteruptiidae)

Gasteruption is an easily recognized genus of wasps whose larvae are predator-inquilines in the nests of cavity-nesting solitary bees (Apidae, Colletidae, Halictidae and Megachilidae), with some records for solitary wasps as hosts (Crabronidae, Vespidae and Sphecidae). There is conflicting information about the biology and host associations for the genus because of a lack of information from the majority of biogeographical regions in the world. Here we concatenate all available literature records pertaining to the biology of adults, host associations and larval development. We conclude that bee hosts are more readily used compared to wasp hosts (71 bee, 13 wasp species), with the majority of wasp observations without sufficient data to be confident of the host association. The majority of known records are for hosts nesting in cavity nests (76 species) rather than ground nests (eight species), with most species recorded from a single host association. From available data, the approximate rates of host nests with parasitized broods are low: 4–7%. We also provide suggestions for improving the quality of future observations in the group.

Daurian redstart Phoenicurus auroreus is a host for the common cuckoo Cuculus canorus during the second, but not the first cultch

Background: Coevolution in cavity-nesting host-cuckoo systems may differ from those in open-nesting hosts due to unique conditions in cavity nests. We investigated brood parasitism in Daurian redstarts ( Phoenicurus auroreus ), a regular cavity-nesting host of common cuckoos ( Cuculus canorus ).Results: A total of 15.6% ( n =358) of host nests were parasitized by cuckoos. Cuckoos were highly successful in parasitizing Daurian redstart nests: nearly all cuckoo eggs were laid in the nest cup, and all cuckoo chicks evicted all host offspring. However, egg ejection by Daurian redstarts was egg morph specific, i.e. hosts laying white eggs ejected most real cuckoo eggs, while hosts laying blue eggs did not eject any. In contrast, hosts ejected most mimetic cuckoo eggs. Moreover, most Daurian redstarts moved to nearby villages during the second breeding attempts, where the risk of cuckoo parasitism was reduced. Parasitism only occurred during the second breeding attempt, since cuckoos had not yet arrived at the breeding grounds when hosts started to lay their first clutches, which may indicate a novel and unique anti-parasite defense, advancing breeding time of hosts.Conclusions: Our results suggest that Daurian redstarts suffer from high risk of cuckoo parasitism showing more intense egg ejection while building nests closer to human habitation in the second clutch. This suggests that cavity-nesting hosts may show adaptations to brood parasites that differ from those of open-nesting hosts.

Recurrent seasonal occurrence of the Lineated Woodpecker (Dryocopus lineatus) in a riparian fragment of the Atlantic Forest, northeastern Brazil

Riparian forests play important roles as ecological corridors and refuge habitat for many bird populations in fragmented landscapes. This report describes the seasonal occurrence of the Lineated Woodpecker (Dryocopus lineatus) in a small riparian fragment of Atlantic Forest, northeastern Brazil. A female was recorded by its visual and acoustical signals from September to October 2014. Similar occurrences were observed in the same months over three consecutive years. Two major hypotheses regarding the woodpecker seasonal occurrence are discussed here: i) the use of the riparian fragment for breeding, evidenced by tree-cavity nests; and ii) fleeing of the bird from its natal habitat due to fire in adjacent sugarcane fields, which commonly are burned in these two months. Such recurrent events suggest that D. lineatus uses the riparian fragment as refuge habitat, highlighting the importance of these environments for bird populations that inhabit fragmented landscapes of the Brazilian Atlantic Forest.

The macroecology of passerine nest types, in the light of macroevolution

Passerine birds build a diversity of nests to lay and incubate eggs, and to house nestlings. Open cup, dome, and hole (or cavity) nests have distinct advantages and/or disadvantages related to predation risk and thermoregulation. We used macroecological and macroevolutionary approaches to test contrasting predictions from considering these consequences. Patterns of prevalence across latitude and elevation for the roofed nest types (holes and domes) provide no evidence that their thermoregulation benefits promote colonization of colder environments. These patterns are more consistent with the role of predation in determining where dome-nesting species in particular occur. Macroevolutionary analyses suggest that diversity patterns for nest types along major ecological gradients mostly arise from how clades with conserved nest types have diversified across gradients, rather than arising from local adaptation. Lastly, we reveal a negative relationship between body mass and latitude in hole-nesting passerines, which runs counter to Bergmann’s rule.Statement of authorshipJPM and JGB designed the study. JPM and ZZ compiled data from the literature. JPM performed statistical analyses with input from JGB. JPM and JGB wrote the manuscript, and ZZ contributed to revisions.Data accessibility statementsData were obtained from existing sources in the literature, cited in the manuscript.

Is the risk of nest predation heterospecifically density-dependent in precocial species belonging to different nesting guilds?

Nest predation is a key source of mortality and variation in fitness, but the effect co-occurring species belonging to different nesting guilds have on each other’s nest success is poorly understood. By using artificial nests, we tested if predation on cavity nests of Common Goldeneyes ( Bucephala clangula (L., 1758)) is increased in the presence of ground nests of Mallards ( Anas platyrhynchos L., 1758) and vice versa. Specifically, by adding ground nests in the vicinity of cavity nests, we tested the hypothesis that predation on cavity nests is heterospecifically density-dependent. A shared predator, the pine marten ( Martes martes (L., 1758)), was intensively hunted in one of the study areas, but not in the other, leading to most individuals in the former being naïve immigrants. Cavity-nest fate was not affected by addition of ground nests. Similarly, ground-nest survival did not decrease when nearby cavity nests were depredated. Fate of nests in a given nest cavity was highly predictable between years in the study area with minimal removal of pine martens, but not in the one with intensive removal. Predation rate was higher on cavity nests than on ground nests. Predation on ground nests was lower in the study area with intensive removal of pine martens. We conclude there was neither apparent competition between guilds nor heterospecific density-dependence in predation risk.