A HYBRID AMAZILIA HUMMINGBIRD FROM HONDURAS

ABSTRACT ∙ We present evidence supporting a hybrid origin of a hummingbird caught in a mist‐net in Reserva Biológica Uyuca, Honduras in 2011. Following a defined diagnostic approach, the individual in question showed intermediate characters in terms of plumage and measurements between Amazilia cyanocephala and A. beryllina, ssp. devillei. The hybrid combination of A. cyanocephala with the nominate subspecies of A. beryllina has been reported once before from Veracruz, Mexico. This is the first time a hybrid of the ssp. devillei – whose taxonomic status is uncertain – with A. cyanocephala is described.RESUMEN ∙ Un colibrí híbrido del género Amazilia de Honduras Presentamos evidencia que respalda el origen híbrido de un colibrí capturado en una red de niebla en Reserva Biológica Uyuca en Honduras en 2011. Según un método establecido de diagnóstico, ese individuo mostró caracteres intermedios en términos de plumaje y medidas morfométricas entre Amazilia cyanocephala y A. beryllina, ssp. devillei. La combinación híbrida entre A. cyanocephala y la subespecie nominal de A. beryllina se ha reportado una vez antes de Veracruz, México. Esta es la primera vez que se describe un híbrido de la ssp. devillei – cuyo estado taxonómico es incierto – con A. cyanocephala

Urbanization has opposite effects on the territory size of two passerine birds

Abstract Background Urban expansion has been identified as one of the leading drivers of biodiversity change or loss. For birds, urbanization is specifically related to survival, breeding success, and territory size. Understanding how different birds adjust territory size in response to urbanization is essential for their conservation in urban environments and to better understand why some species are lost and others persist under this condition. We evaluated the effect of urbanization on the territory size of an urban avoider species, White-eared Ground-Sparrow (Melozone leucotis), and an urban adapter species, House Wren (Troglodytes aedon), at five Costa Rican sites. Methods We measured the size of 30 ground-sparrow and 28 wren territories using a total of 296 h of observation. We followed each individual for at least 1 h per day for at least 2 days of two consecutive years, and geo-referenced their locations. Territory size was estimated using the minimum convex polygon method. We measured the urban surfaces (roads, buildings, any other paved area, soccer fields, lawns, and gardens with short grass) within territories. Results Ground-sparrow territories were larger at the highly urbanized site than at the non-urbanized site. Wren territories were larger at the low urbanized site than at the highly urbanized site. We found a positive relationship between urban surface and territory size for the ground-sparrow, but not for the wren. Conclusions Our results showed that not all birds adjust territory size in the same way in response to urbanization. We showed that urban avoiders probably need to defend larger territories in urban environments to find all the resources required to survive because urban environments may provide insufficient resources such as food or shelter. Urban adapters on the other hand defend smaller territories in urban environments because even small territories may provide sufficient resources. These results suggest specific behavioral adaptations developed by Neotropical birds inhabiting urban environments

Surviving in cities: the case of a year-round territorial bird in the Neotropics

Urban expansion has been identified as one of the main threats to biodiversity because it can negatively affect wildlife populations. However, wildlife population dynamics have not been studied in one of the most rapidly urbanizing regions in the world—the Neotropics. To examine the effect of urbanization on the population dynamics of Neotropical wildlife, we used recapture data from a marked population (2011–2017) of White-eared Ground-Sparrow (Melozone leucotis) across an urban–rural gradient in the Costa Rican Central Valley. Additionally, we tested if this effect differed between males and females. Contrary to our prediction, ground-sparrow survival rates were higher in urban and suburban sites than in the rural site, and we found that survival was positively correlated to the proportion of urban surface inside each territory (b¼0.90, 95% CI: 0.71–0.97). We did not find differences in survival rates between the sexes and the mean survival rate was high overall (0.7960.06). Surprisingly, our results suggest that the survival rate of this urban avoider is positively influenced by urbanization, and therefore, suggest that the potential cost to some urban avoiders may not be driven by reduced survival in more urbanized environments, and could be driven by reductions in other vital rates. Therefore, we encourage research to evaluate multiple vital rates of urban avoiders and urban adapters to achieve more comprehensive knowledge on how urbanization is affecting avian populations in the Neotropics.Universidad de Costa Rica/[111-B5-241]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Territory size, population density, and natural history of Cabanis’s Ground Sparrow, an endemic species found in urban areas

Worldwide urban expansion threatens biodiversity inhabiting the original natural environments now being transformed, especially range-restricted species. Here, we provide estimates of population density, population size, and territory size of Cabanis’s Ground Sparrow Melozone cabanisi, a Costa Rican endemic. Additionally, we provide information about its life history. We measured abundance and estimated density using the King model. We estimated population size using density data and available habitat. We estimated territory size by following 21 pairs during the breeding season. We followed every individual for 1–3 days, for at least 1 h per day, and geo-referenced their locations. We then estimated territory size using the minimum convex polygon method. Counts and territory size observations were carried out between 06:00 and 09:00 h, when this species is most active. We summarized natural history from opportunistic observations collected during 20 years in the field as well as data from museum specimens. Bird densities range from 0.06 to 0.24 mature individuals per hectare. We estimated that the global population of Cabanis’s Ground Sparrow is between 2958 and 11,832 mature individuals. Territory size was larger at the suburban and urban sites than at the rural sites. The breeding season for this species spans 10 months with a peak in June–July. Nest architecture is less variable than that reported for other congeners. Both parents feed and defend their nestlings and provide nest sanitation. Since we found lower bird density and larger territory size at the suburban and urban sites, we propose that these represent lower-quality habitats for Cabanis’s Ground Sparrows. Given its small population size, the reduction and fragmentation of its habitats due to urbanization, and its high conservation priority assigned by the Costa Rican government, we urgently recommend a careful re-evaluation of the species’ IUCN status.Universidad de Costa Rica/[111-B9-469]/UCR/Costa RicaUniversidad de Costa Rica/[111-B9-123]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

House Wrens Troglodytes aedon reduce repertoire size and change song element frequencies in response to anthropogenic noise

Anthropogenic noise (≤ 3 kHz) can affect key features of birds’ acoustic communication via two different processes: (1) song-learning, because songbirds need to hear themselves and other birds to crystallize their song, and (2) avoidance of song elements that overlap with anthropogenic noise. In this study we tested whether anthropogenic noise reduces the number of song elements in the repertoire of House Wren Troglodytes aedon, an urban species. Additionally, we tested whether the proportion of high-frequency elements (i.e. elements where the minimum frequency is above 3 kHz) is related to anthropogenic noise levels, and how the frequencies and duration of shared elements between males change with different levels of anthropogenic noise. We recorded 29 House Wren males exposed to different anthropogenic noise levels (36.50-79.50 dB) during two consecutive breeding seasons from four locations. We recorded each male on 2 days during each season continuously for 50 min (we collected 104 h of recordings) and measured anthropogenic noise levels every 10 min inside each male territory during the recording period. In general, individuals inhabiting noisier territories had smaller repertoires. However, only in two locations with anthropogenic noise levels between 38.60 and 79.50 dB did males inhabiting noisier territories have smaller repertoires. In the other two locations with lower anthropogenic noise (36.50-66.50 dB), the anthropogenic noise inside each territory was not related to the repertoire size. Individuals inhabiting the noisiest location showed a tendency to include more high-frequency elements in their songs. In 26% of the elements, the anthropogenic noise affected their frequency features. Our results showed that not all House Wrens inhabiting urban environments modify their songs at the highest level of organization (i.e. repertoire) to reduce the masking effect of anthropogenic noise on acoustic communication.Universidad de Costa Rica/[111-B5-241]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Different Messages are Transmitted by Individual Duet Contributions and Complete Duets in a Species with Highly Overlapped Duets

Background: Duet function hypotheses have been mostly studied in bird species that produce duets with male and female solo songs. However, in order to understand if patterns of duet function are similar across all duetting species, it is highly necessary to test the duet function hypotheses in species that produce duets with vocalizations other than solo songs. Objective: We studied the responses of territorial pairs to each sex’s individual duet contribution and complete duets in a species that produces duets with a vocalization other than male and female solo songs. Methods: We conducted a playback experiment where we presented duet contributions of each sex to three populations of White-eared Ground-sparrows (Melozone leucotis) in Costa Rica, during this species’ breeding season in 2016. Results: The responses to complete duets were stronger than those to each sex’s duet contribution, suggesting that complete duets and each sex’s duet contribution have different functions. Complete duets are used to protect resources from intruders (supporting the resource defense hypothesis), and to prevent the partner from being usurped by intruders (supporting the mate-guarding hypothesis). Males used solo songs in response to female duet contributions, and this may work to attract intruder females (increasing the probability of extra-pair copulation). Males also use solo songs in response to male duet contributions, which may work as a signal to repel intruder males and guard their female. In this case, where mate attraction occurs with a completely different type of vocalization than used for duetting, we found a clear pattern of a double agenda for males when a territorial intrusion occurs. Conclusions: This study provides strong support for the dual function hypothesis in duets and reveals conflicting selective pressures between pair members relative to each hypothesis.Universidad de Costa Rica/[111-B5-241]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí