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Harrison’s rule, that body size is positively correlated between parasites and hosts, has been reported in a range of taxa, but whether the rule is applicable to cleptoparasitic insects is poorly understood. Subfamily Nomadinae, the largest group of cleptoparasitic bees, usurp the nests of a variety of host bees. Within the subfamily, Nomada exploits the most diverse hosts, using at least ten genera from five families. Here, we reassess the phylogeny of Nomadinae, including the expanded sampling of the genus Nomada , to explore host shift fluctuations throughout their evolutionary history and test the applicability of Harrison’s rule for the subfamily. Our phylogenetic results are mostly congruent with previous investigations, but we infer the tribe Hexepeolini as a sister taxon to the tribe Nomadini. Additionally, the results reveal discrepancies with the traditional classifications of Nomada . Ancestral state reconstruction of host use indicates that, early in their evolution, parasites used closer relatives, before attacking less related groups later. Lastly, we confirm Harrison’s rule in Nomadinae, supporting that body size dynamics influence the host shifts of cleptoparasitic bees.

Objectives: This study aims to identify and analyse the forms of infringement on the sovereign right of public authority in the issuance and management of currency, particularly in the context of the fractional reserve banking system and the technological advancements facilitated by globalisation, which have enabled the creation and promotion of virtual currencies. Methodology: The study adopts a composite method that combines historical induction and logical reasoning to explore the forms of infringement on the general jurisdiction of the authority associated with both traditional and emerging forms of currency. Findings: The study concludes that safeguarding public authority's exclusive and disinterested right in currency issuance and management is a priority in Islamic legal policy. Such necessitates caution against forms of infringement that violate this right due to their impact on the fairness and efficiency of the monetary system. Originality: This research's originality lies in its characterisation of the generation of credit money and the issuance or mining of virtual currencies as contemporary forms of infringement on the authority's general jurisdiction, akin to the counterfeiting of paper money.

We investigated the usurpation behavior of the hornet Vespa basalis Smith in nests of V. velutina Lepeletier. We collected 47 nests of the two species in Taiwan in their establishment and growth stages. Of these, 29 were mixed-species nests, and in at least 16 V. velutina was replaced by V. basalis . While most nests were initiated by V. velutina , V. basalis coexisted with it during the establishment stage, leading to intense conflict between the two. The multiplex PCR method gave evidence of the usurper’s eggs and larvae in the mixed-species nest. Over time, the number of adults and brood in usurped V. velutina nests decreased, while those of V. basalis increased, demonstrating behavior in V. basalis akin to facultative social parasitism. This study provides further evidence of nest usurpation in the genus Vespa , along with description of complex interactions among these hornets, their natural enemies, prey, and humans in Taiwan.

Some birds cover their eggs with nest material when they leave to forage. It has been suggested that such egg-covering aids thermoregulation or prevents predation but here we present a new hypothesis, that secondary cavity-nesting species cover their eggs to prevent nest usurpation by other birds. When the bottom of the cavity is dark, as when eggs are covered by nest material, it may be difficult for a prospecting competitor to see whether a defending nest owner or a predator is hiding inside the cavity. Competitors may therefore hesitate to enter dark cavities. We filmed 21 great tit (Parus major) nests during the egg-laying period and found that the female spent bouts of highly variable length outside the nest box (range 0.3–250 min, n = 51), so prospecting small passerines would have difficulty predicting whether an aggressive tit owner was in the box or would soon return. We presented prospecting male pied flycatchers (Ficedula hypoleuca) with a dyad of boxes (n = 93), each containing a great tit nest but only one with visible eggs. Flycatchers hesitated more to enter a nest box with no visible tit eggs than a box with exposed eggs. This was most evident for nest boxes with dark versus light interior paint, supporting the idea that better interior illumination makes prospecting birds more confident about entering an unfamiliar cavity. The usurpation and predation hypotheses are not mutually exclusive because both competitors and small predators may hesitate to enter dark, enclosed spaces if visibility is low.

Some secondary cavity-nesting birds use nest material to cover their eggs when they are out foraging during the egg-laying stage. Egg covering presumably helps regulate nest temperature and/or prevents predation or parasitism. A recent study suggested that egg covering might prevent nest usurpation and therefore, we set up nest boxes with three different treatments to test this hypothesis: bottom of the nest box covered with moss containing two eggs covered with moss (type A); floor of the nest box covered with moss and two eggs exposed on top of the moss (Type B); and bare floor of the nest box, with two eggs added (Type C). The results showed the lowest egg predation rates in Type A nest boxes, which was significantly lower than those in type C boxes; the proportion of maritime striped squirrels (Tamiops maritimus), first appearing in the three types of nest box was not significantly different; however, the rate of first entry into Type A was significantly lower than that into Type C boxes. The rate of first entry and the time the squirrels spent in Type A boxes were significantly lower and shorter than those in Type C boxes. Our results suggest that the egg-covering behavior of secondary cavity-nesting birds delayed the entry of nest competitors and accelerated the departure of nest encroachers from the nest, thus provided experimental evidence for the usurpation hypothesis.Significance statementSeveral non-mutually exclusive hypotheses have been proposed to explain the function of egg covering by bird species. The present study showed that egg covering by secondary cavity-nesting birds delayed the entry of maritime striped squirrels and accelerated the departure of nest encroachers from the nest, suggesting that egg covering might reduce the cost of nest defense for birds and thus prevent nest encroachment by other species. We provided experimental evidence for the new hypothesis proposed by Slagsvold and Wiebe (2021a) that egg-covering behavior of birds deters nest encroachers from easily entering unfamiliar, poorly lit cavities due to fear, thereby effectively preventing nest usurpation by squirrels.

Interspecific nest usurpation, a relatively common nesting strategy, is the act of one bird species taking over the nesting site of another species. Although used by secondary cavity-nesters, nest usurpation has never been reported for the Tufted Titmouse (Baeolophus bicolor). In this paper, we document a mixed brood successfully reared by Tufted Titmice after usurpation of an Eastern Bluebird (Sialia sialis) nest in northeastern Arkansas during the 2019 breeding season. We monitored the focal nest box every 3–4 d from the first sign of nest building on 23 March 2019 until chick fledging by 12 May 2019. The Tufted Titmice took over the nest at the time the Eastern Bluebird had laid its fourth egg in the nest. By the end of the nesting period, the Tufted Titmice fledged 2 of their own chicks and 3 Eastern Bluebird chicks. Such successful rearing of non-conspecific nestlings is rare and we discuss factors that may have allowed it.

Cities are hotter, more fragmented, and less vegetated habitats than surrounding semi-natural areas. While such urban conditions have been shown to affect a variety of morpho-physiological traits in wild bees, potential effects on behavior have not been investigated. Behavioral plasticity may be a predictor of species success in urban matrices as more aggressive individuals may be advantaged in competitive contexts. Here, the behavioral plasticity (frequency of aggressive, avoidance, and tolerant behaviors during female-female interactions) of the solitary bee Osmia cornuta was tested using circle-tube experiments at four sites in Milan (Italy) to test the hypothesis that higher levels of urbanization (as defined by shifts in temperature and land-use change) increase intra-specific aggression. The behavioral profile of O. cornuta was largely dominated by aggressive interactions towards conspecifics at all sites (likely due to nest usurpation). However, behavioral variation was observed across the studied sites. First, aggression increased with mean site temperature (likely due to the heat stress caused by the Urban Heat Island effect). Bees tested later in the morning (at hotter times of the day) were also more aggressive. Second, bees were more likely to avoid interacting in greener, less urbanized areas. Additionally, larger differences in body size between paired bees also increased aggression, possibly because larger individuals are more prone to attack smaller ones. Although a larger urban gradient is needed to confirm these findings, the results suggest a shift towards more aggressive behavior in solitary bees exposed to higher levels of urbanization, similar to what has previously been observed in some vertebrates and spiders in urban habitats.

Abstract Infanticide has been described across mammal species. Infanticide is thought to be a tactic which increases reproductive opportunities or reduces competition over local resources. Species of the genus Equus exhibit life history traits such as expensive young, long gestation, lactation and dependency, extended inter-birth interval when there is a foal at foot and strong male reproductive skew. These traits suggest infanticide may be present throughout the genus. However, most documented cases of infanticide attempts come from captive populations and rely heavily on indirect accounts in free-roaming populations. Here, we report an infanticide attempt in Cape mountain zebra (Equus zebra zebra). The aggression was perpetrated by multiple bachelor males on two foals belonging to the same family group. The foals were separated from the parent group, chased and harried for a total of 45 minutes before the mothers and herd stallion were able to regain their offspring. We also report three cases of infanticide from necropsy. The injuries sustained by the foals are consistent with infanticide-based injuries documented in other equids species. The timing of these deaths occurs after a stallion turnover. These two cases provide the most conclusive evidence to date that infanticide takes place within mountain zebra.

We observed a Killdeer (Charadrius vociferus) incubating a nest containing 1 Piping Plover (Charadrius melodus) egg and 2 Killdeer eggs at a sand and gravel mine in West Point, Nebraska. Four days later, the nest contained 1 Piping Plover egg and 4 Killdeer eggs. Two days later, the Piping Plover egg was absent, and the 4 Killdeer eggs remained in the nest. Eight days later the nest was destroyed. We speculate the nest began as a Piping Plover nest and was usurped by a Killdeer pair. To our knowledge, this is the first documentation of a nest containing eggs from both species. Observamos a un chorlito Charadrius vociferus incubando un nido que contenía 1 huevo de chorlito Charadrius melodus y 2 huevos de chorlito C. vociferus en una mina de arena y grava en West Point, Nebraska. Cuatro días despúes, el nido contenía 1 huevo de chorlito C. melodus y 4 de chorlito C. vociferus. Dos días después, el huevo de chorlito C. melodus estaba ausente y los 5 huevos de chorlito C. vociferus permanecían en el nido. Ocho días después el nido fue destruido. Especulamos que el nido inició como nido de chorlito C. melodus y fue usurpado por una pareja de chorlito C. vociferus. Por lo que sabemos, este es el primer caso documentado de un nido que contenía huevos de ambas especies. Palabras clave: Charrán menor, minas de arena y grava, monitoreo de nidos de aves costeras, Platte River, Sternula antillarum, usurpación de nido.

With the exception of a few groups of birds, such as large raptors and colonial seabirds, direct counts of nests cannot be conducted over very large areas for most of the abundant and widely distributed species, and thus indirect methods are used to estimate their relative abundances and population sizes. However, many species of the Family Hirundinidae (swallows and martins) build their mud nests in discrete, predictable and accessible sites, which are reused across years. Therefore, the direct count of active nests could constitute a reliable method for estimating breeding population sizes and their changes at large spatial and temporal scales. We illustrate the feasibility of this monitoring approach through a single year survey of >2700 nests of three coexisting Old‐World species, the barn swallow (Hirundo rustica), the red‐rumped swallow (Cecropis daurica), and the crag martin (Ptyonoprogne rupestris), distributed across Portugal and Spain. Our results revealed changes in the use of nesting substrates and increases in interspecific nest usurpation rates over recent decades. While 56% of the nests of C. daurica were located in rocks five decades ago, almost 100% are nowadays located in anthropogenic substrates such as bridges, road culverts, and abandoned buildings, which could have favored the range expansion of this species. Nest occupation rates were surprisingly low (12% in C. daurica, 21% in H. rustica, and 37% in P. rupestris), and the proportion of abandoned nesting sites was very high (65% in C. daurica, 50% in H. rustica, and 27% in P. rupestris). Abandonment rates reflect the population decline reported for H. rustica. Notably, the usurpation of nests of C. daurica by house sparrows Passer domesticus, which is the main cause of breeding failure, has increased from 2.4% in 1976–1979 to 34.7% of the nests nowadays. The long‐term monitoring of nests may constitute a reliable and affordable method, with the help of citizen science, for assessing changes in breeding population sizes and conservation threats of these and other mud‐nest building hirundines worldwide. The long‐term monitoring of nests may constitute a reliable and affordable method, with the help of citizen science, for assessing changes in breeding population sizes and conservation threats of mud‐nest building hirundines worldwide. Breeding adults, and completely built and destroyed nests of red‐rumped swallows Cecropis daurica (a1–a5), barn swallows Hirundo rustica (b1–b5), and rock martins Ptyonoprogne rupestris (c1–c5), with scales for size comparisons. Photographs: José L. Tella.