We explored the relationship between haemosporidian infection (infected vs. uninfected), parasite load, heterophil:lymphocyte ratio, body condition and vocal behaviour of the Rufous‐naped Wren ...Campylorhynchus rufinucha. Our results, albeit based on a small sample size, showed no evidence of an association between vocal behaviour and infection status, heterophil:lymphocyte ratio or body condition. Infections did not vary between localities. Our results showed, however, that infection status was associated with a higher song rate, and that in males and females belonging to the same reproductive pair there was a strong positive correlation in terms of infection status and parasite load.
En este estudio exploramos la relación entre la infección por hemosporidios (infectados vs. no infectados), la carga parasitaria, la proporción de heterófilos‐linfocitos, la condición corporal y el comportamiento vocal de la Matraca Nuca Canela Campylorhynchus rufinucha. Nuestros resultados, aunque basados en un tamaño de muestra pequeño, no mostraron evidencia de una asociación entre el comportamiento vocal y el estado de infección, la relación heterófilo:linfocito, o la condición corporal. Las infecciones no variaron entre las localidades. Sin embargo, nuestros hallazgos mostraron que las aves infectadas tenían una mayor tasa de canto que las no infectadas, y que los machos y las hembras pertenecientes a la misma pareja reproductiva tenían una fuerte correlación positiva en el estado de infección y la carga parasitaria.
We addressed the role of nocturnal singing in the diurnal field sparrow, Spizella pusilla. We were particularly interested in whether nocturnal song is used to repel intruders (intrasexual function) ...and/or to attract females seeking extrapair copulations (intersexual function). First, we used autonomous acoustic recording units (ARUs) and an automated detection and classification system to examine the associations of singing behaviour of mated field sparrows with social factors (fertility stage, presence of neighbour song and presence of intruder song). Second, using an automated radiotelemetry system (ARTS), autonomous acoustic recording units (ARUs) and automated playback systems, we conducted a nocturnal playback experiment to explore how mated male and female field sparrows respond to nocturnal songs at night and across prefertile, fertile and postfertile stages. We found that neighbours and intruder males tended to sing complex songs on the same nights when focal males sang. While not all focal males sang at night, all male birds (resident males, neighbours and intruders) that sang tended to sing according to the fertility periods of the resident male's female. Our playback experiment demonstrated that, although field sparrows usually slept and were inactive at night, they moved in response to nocturnal field sparrow songs more than to control stimuli (other species vocalizations). Interestingly, we found that males did not respond by singing or countersinging to field sparrow nocturnal songs (simulated intrusions). We also demonstrated that male activity responses were similar during the prefertile and postfertile stages, while females responded more during the prefertile and fertile stages than during the postfertile stage. Consequently, the nocturnal song in the field sparrow appears to play a role in extrapair mate attraction (intersexual function) more than in repelling intruders (intrasexual function). While nocturnal singing is an infrequent behaviour of most diurnal birds, it may be important in the mating system of these birds.
•We examined whether nocturnal field sparrow song serves to attract extrapair females.•Mated males, including male neighbours and intruders, sang when females were fertile.•Mated males did not sing in response to playbacks of simulated intruders.•Mated females actively responded to playbacks of nonsocial mates at night.•Mated females responded more strongly to nocturnal songs when they were fertile.
Abstract
Background
Among urban stimuli, anthropogenic noise has been identified to be one of the behavioral drivers of species that rely on acoustic signals for communication. Studies have shown ...both species-specific and assemblage responses to urban noise, ranging from the modulation of their acoustic frequencies and spatiotemporal adjustments to declines in species richness. In this study, we assessed the citywide relationship between two anthropogenic noise variables (noise levels recorded during bird surveys and daily average noise levels) and vegetation cover with bird species richness.
Methods
This study was conducted in the city of Xalapa (Mexico) through a 114 citywide point-count survey. We recorded bird communities at each sampling site. We measured noise levels using a sound level meter while performing point-counts. Then, we generated a map of average daily noise of the city using an array of 61 autonomous recording units distributed across the city of Xalapa and calculated daily noise levels for the 114 points. We ran a linear model (LM) to assess potential relationships between both point-count and daily (24 h) noise values and vegetation cover with bird richness.
Results
Results from the LM show: (1) a negative relationship between maximum point-count noise and avian species richness, (2) no relationship between 24 h noise and bird species richness, and (3) a positive relationship between vegetation cover and bird species richness.
Conclusions
Results provide evidence that decreases in urban bird species richness do not necessarily imply the permanent absence of species, suggesting that birds can temporarily fly away from or avoid sites when noisy, become cryptic while noisy events are occurring, or be undetected due to our inability to record them in the field during noisy events.
In this study we focused on urban bird diversity across Mexico, a megadiverse country, with a special focus on the relative role of urban greenspaces and heavily-built sites. We considered a ...country-wide approach, including 24 different sized Mexican cities. Our aims were to describe the urban bird diversity in focal cities and further assess the relationships between it and the biogeographic region where cities are located, their size, elevation, and annual rainfall. Additionally, we evaluated differences in the functional composition of bird communities in both studied urban scenarios (i.e., urban greenspaces, heavily-built sites). Our results confirm that urban greenspaces are home to a large proportion of species when contrasted with heavily-built sites. While total species richness and species richness of greenspaces were related with the cities' biogeographic region –with higher species richness in the Neotropical region and Transition Zone–, the relationship did not hold true in heavily-built sites. We found that annual rainfall was negatively related to bird richness in heavily-built sites, suggesting that species from arid systems can be more tolerant to urbanization. Regarding the bird functional group assessment, results show a clear differentiation between the functional groups of greenspaces and those of heavily-built sites, with granivores and omnivores associated with the latter and a highly diverse array of functional groups associated with urban greenspaces.
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•Urban greenspaces are home to many more species, in general, than heavily-built sites.•Total urban bird richness and that of greenspaces were related to biogeographic region.•Annual rainfall negatively associated with bird richness in heavily-built sites.•Bird functional groups differed between urban greenspaces and heavily-built sites.•A highly diverse array of functional avian groups was found in urban greenspaces.
Interspecific territoriality is frequently reported between closely related species; however, few studies have demonstrated interspecific territoriality between distantly related species living in ...sympatry. We conducted playback experiments to investigate territorial behaviour in male and female White‐bellied Wrens (Uropsila leucogastra) in response to simulated conspecific and heterospecific intruders during the breeding and non‐breeding seasons. We explored whether heterospecific songs of the Happy Wren (Pheugopedius felix), a distantly related species and ecological competitor, elicited antagonistic responses from focal White‐bellied Wrens, and whether such responses differed between the sexes. We also examined whether male and female responses to conspecific and heterospecific rivals varied with season. We found that male White‐bellied Wrens always responded to conspecific song, and responded significantly more to heterospecific song compared to a control stimulus (Tropical Parula, Setophaga pitiayumi). In contrast, although female White‐bellied Wrens responded strongly to conspecific song, their response to heterospecific song did not differ significantly from the control stimulus. The proportion of males that responded to heterospecific songs and the proportion of females that responded to conspecific songs varied seasonally, showing significantly lower responses during the breeding season. The intense responses of male White‐bellied Wrens to playback of heterospecific songs suggest that they recognise ecological competitors based on their vocal signals. Furthermore, the decrease in agonistic interactions during the breeding season is in line with the hypothesis that aggressive behaviour may be detrimental to reproductive and parental activity, and the hypothesis that heterospecific animals pose less of a threat during the breeding season.
Studies of geographic variation of bird vocalizations facilitate the understanding of species' divergence and evolutionary histories, as vocal traits vary in response to different factors including ...the environment, morphology, culture, and inheritance. The Acorn Woodpecker (Melanerpes formicivorus) is a non-passerine species of the family Picidae, and therefore its vocalizations are not acquired through learning. It is widely distributed throughout the Americas and exhibits distinctive morphological and genetic differences among the 7 allopatric subspecies, but little is known about geographic variation in the structure of its vocalizations and whether vocal variation corresponds with their genetic differences. We collected recordings throughout the species' range and assessed the frequency and temporal features of their most common calls to study geographic variation in vocalizations. Specifically, we tested whether divergence in vocal traits mirrored subspecies limits. Our results showed the formation of 2 vocal groups that do not reflect subspecies limits. The genetic divergence described in previous studies coincides with the vocal divergence found in this study, with 2 areas promoting the greatest divergence: the Isthmus of Tehuantepec and the Gulf of California. Previously described morphological variation in bill sizes also coincides with the vocal groups found in this study, in which large and small sizes are grouped separately.
Phenotypic traits such as songs are important in species recognition. Variation in acoustic traits can form barriers to gene flow and promote speciation. Therefore, understanding song divergence is ...crucial in groups with controversial taxonomy such as Olive Sparrows (Arremonops rufivirgatus), a widespread Neotropical species of songbird with multiple allopatric populations. Taxonomic authorities disagree on the number of Olive Sparrow subspecies, placing them into either two or three main groups. These groups may represent separate species based on morphological traits, but trait divergence within the complex has not been examined. We studied geographic variation in the characteristics of the songs of Olive Sparrows at two geographical levels: among three proposed groups and among five allopatric populations. In a second analysis, we evaluated the strength of acoustic divergence within the complex by comparing acoustic distances among groups and allopatric populations of Olive Sparrows with the acoustic distance among three recognized species in the genus Arremonops. We analyzed 802 songs from 174 individuals across 81 locations and measured 12 variables to describe the fine structural characteristics of the songs of Olive Sparrows, Green-backed Sparrows (A. chloronotus), Black-striped Sparrows (A. conirostris), and Tocuyo Sparrows (A. tocuyensis). We found significant acoustic variation in the Olive Sparrow complex at both geographical levels. Our divergence analysis also revealed that vocal divergence within the complex is similar to or greater than that found between recognized species in the genus. Together, these results suggest that acoustic diversity within the Olive Sparrow complex probably originated by isolation in tandem with selective and/or non-selective factors.
Los caracteres fenotípicos, como los cantos, son importantes para el reconocimiento de especies. La variación en caracteres acústicos puede formar barreras que previenen el flujo genético y promueven especiación. Por lo tanto, es crucial entender la divergencia en el canto en grupos en los cuales la taxonomía es controversial como en Arremonops rufivirgatus, una especie de ave canora Neotropical, ampliamente distribuida con múltiples poblaciones alopátricas. Las autoridades taxonómicas están en desacuerdo con respecto al número de subespecies de Arremonops rufivirgatus, ubicándolas en dos o tres grupos principales. Estos grupos pueden representar especies diferentes basado en caracteres morfológicos, pero la divergencia dentro del complejo no ha sido evaluada. Nosotros estudiamos la variación geográfica en las características del canto de Arremonops rufivirgatus en dos niveles geograficos: a través de los tres grupos propuestos y a través de cinco poblaciones alopátricas. En un segundo análisis, evaluamos la magnitud de la divergencia acústica dentro del complejo, comparando distancias acústicas entre los grupos y las poblaciones alopátricas de Arremonops rufivirgatus con la distancia acústica entre tres especies reconocidas en el género Arremonops. Analizamos 802 cantos de 174 individuos a través de 81 localidades y medimos 12 variables para describir las características estructurales finas de los cantos de Arremonops rufivirgatus, A. choloronotus, A. conirostris y A. tocuyensis. Nosotros encontramos variación acústica significativa en el complejo de Arremonops rufivirgatus en los dos niveles geográficos. Nuestros análisis revelaron que la divergencia local dentro del complejo es similar o mayor que la encontrada entre especies reconocidas en el género. Estos resultados sugieren que la diversidad acústica dentro del complejo de Arremonops rufivirgatus se originó probablemente por aislamiento geográfico en tándem con factores selectivos y/o no-selectivos.
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