Urban Noise Restricts Song Frequency Bandwidth and Syllable Diversity in Bananaquits: Increasing Audibility at the Expense of Signal Quality

Anthropogenic noise can interfere with animal behavior through masking of acoustic communication. In response to masking, animals may change their acoustic signals as an apparent adjustment strategy, but this may have a drawback on signal quality. Songs and calls may show noise-dependent changes in frequency and duration, which may yield some masking avoidance, but may also constrain other acoustic parameters that might carry information about the sender. In the present study, we investigated whether noise-dependent reduction in frequency bandwidth or song duration restricted syllable diversity or song elaboration in a Neotropical songbird, the bananaquit (Coereba flaveola). We show that bananaquits sing higher frequency songs, of narrower bandwidth, in noisier territories, independent of variation in territory density, without significant variation in song duration. We also show that songs with higher minimum frequencies, narrower bandwidths, and shorter durations have on average a lower number of syllable types and higher syllable rates. This finding is in line with an acoustic restriction and may reflect a functional trade-off between audibility and signal value: higher frequencies may be more audible but less elaborate songs may weaken the message of sender quality. Consequently, noise pollution may not only alter avian communities, but also shape acoustic diversity and processes of sexual selection in urban environments.

Effects of seed-rich habitat provision on territory density, home range and breeding performance of European Turtle Doves Streptopelia turtur

Summary Conservation measures providing food-rich habitats through agri-environment schemes (AES) have the potential to affect the demography and local abundance of species limited by food availability. The European Turtle Dove Streptopelia turtur is one of Europe’s fastest declining birds, with breeding season dietary changes coincident with a reduction in reproductive output suggesting food limitation during breeding. In this study we provided seed-rich habitats at six intervention sites over a 4-year period and tested for impacts of the intervention on breeding success, ranging behaviour and the local abundance of territorial turtle doves. Nesting success and chick biometrics were unrelated to the local availability of seed-rich habitat or to the proximity of intervention plots. Nestling weight was higher close to human habitation consistent with an influence of anthropogenic supplementary food provision. Small home ranges were associated with a high proportion of non-farmed habitats, while large home ranges were more likely to contain seed-rich habitat suggesting that breeding doves were willing to travel further to utilize such habitat where available. Extensively managed grassland and intervention plot fields were selected by foraging turtle doves. A slower temporal decline in the abundance of breeding males on intervention sites probably reflects enhanced habitat suitability during territory settlement. Refining techniques to deliver sources of sown, natural, and supplementary seed that are plentiful, accessible, and parasite-free is likely to be crucial for the conservation of turtle doves.

Impact of a recolonizing, cross-border carnivore population on ungulate harvest in Scandinavia

Predation from large carnivores and human harvest are the two main mortality factors affecting the dynamics of many ungulate populations. We examined long-term moose (Alces alces) harvest data from two countries that share cross-border populations of wolves (Canis lupus) and their main prey moose. We tested how a spatial gradient of increasing wolf territory density affected moose harvest density and age and sex composition of the harvested animals (n = 549,310), along a latitudinal gradient during 1995–2017. In areas containing average-sized wolf territories, harvest density was on average 37% (Norway) and 51% (Sweden) lower than in areas without wolves. In Sweden, calves made up a higher proportion of the moose harvest than in Norway, and this proportion was reduced with increased wolf territory density, while it increased in Norway. The proportion of females in the adult harvest was more strongly reduced in Sweden than in Norway as a response to increased wolf territory density. Moose management in both countries performed actions aimed to increase productivity in the moose population, in order to compensate for the increased mortality caused by wolves. These management actions are empirical examples of an adaptive management in response to the return of large carnivores.

Distribution and habitat of Australian Pied Oystercatchers Haematopus longirostris along the SE Australian coast

SUMMARYAustralian Pied Oystercatchers Haematopus longirostris and their habitat were surveyed on 72 beaches and 674 km of the SE Australian Coast, from Fraser Island, Queensland to near the New South Wales–Victoria state border and between 2015–2018. A grand total of 41 oystercatcher territories and 232 individual birds (the sum of mean beach counts) were counted. Bird-habitat models for oystercatcher mean count density indicated a positive response to the abundance of the primary prey species Donax deltoides, a large ‘surf clam’ and commonly known as the ‘pipi’, a negative response to the proportion of beach length urban and a negative S-N trend. Models for oystercatcher territory density indicated a positive response to pipi abundance and a negative response to pedestrian access density. This report upgrades the coastal development, tourism and human recreation disturbance threats for the species and calls for the long term protection of beach-nesting bird habitat.

Short-term riparian restoration success measured by territory density and reproductive success of three songbirds along the Trinity River, California

Water crises and endangered salmon are pressing environmental concerns influencing restoration decisions in the western United States. When instream restoration necessitates initial loss of riparian cover to restore floodplain function, a short-term goal to minimize harm to riparian-associated wildlife is a worthwhile benchmark. From 2012 to 2015, we examined short-term restoration success, as measured by territory characteristics and reproductive success in restored and reference sites, for 3 riparian bird species (Song Sparrow [Melospiza melodia], Yellow-breasted Chat [Icteria virens], and Yellow Warbler [Setophaga petechia]) along a 64 km stretch of the Trinity River, California. Territory size had the highest relative variable importance in sets of candidate models explaining territory density for all 3 species, and was inversely related to territory density for each. The effect of site type (i.e. restored vs. reference) in explaining territory density was least for Song Sparrow, greater for Yellow Warbler (for which density was 1.4 times greater on reference sites), and greatest for Yellow-breasted Chat (which were more than twice as dense on reference sites). While territory density and mean territory size were inversely related, we found no relationship between territory density or site type and mean productivity per nest, and nest success did not differ between restored and reference sites for any species. In combination, these results suggest that restoration has achieved short-term success as measured by reproductive success, but has not yet been fully successful in supporting similar territory densities as reference sites. In order to determine whether long-term restoration goals are fully achieved, future research should continue to measure density of the 3 focal species as vegetation on the replanted floodplains matures.

Breeding density of the Tawny Owl Strix aluco in urban forests of Ljubljana City (Central Slovenia)

SummaryResults of the survey carried out in the territories of Tawny Owl Strix aluco in Ljubljana urban forests (Tivoli, Rožnik and Šišenski hrib Nature Park and Golovec Hill) were compared with the species territory density in non-urban forest of Mt. Krim. Surveys were performed with the point count method using playback in the springs of 2002 and 2016. The density established at Golovec Hill was 9.3 territories / 10 km2, while in Tivoli, Rožnik and Šišenski hrib Nature Park it reached 10.4 territories / 10 km2, which was higher than at Mt. Krim (4.1-5.8 territories / 10 km2), although densities between sites were not statistically different. Based on our surveys, the estimated population size of the urban Tawny Owl in Ljubljana would consist of 57 to 65 pairs. Our results suggest that the Tawny Owl can adapt well to the living conditions in the city urban forests and indicate the importance of the forest patches in urban areas.

Louisiana Waterthrush and Benthic Macroinvertebrate Response to Shale Gas Development

Because shale gas development is occurring over large landscapes and consequently is affecting many headwater streams, an understanding of its effects on headwater-stream faunal communities is needed. We examined effects of shale gas development (well pads and associated infrastructure) on Louisiana waterthrush Parkesia motacilla and benthic macroinvertebrate communities in 12 West Virginia headwater streams in 2011. Streams were classed as impacted (n = 6) or unimpacted (n = 6) by shale gas development. We quantified waterthrush demography (nest success, clutch size, number of fledglings, territory density), a waterthrush Habitat Suitability Index, a Rapid Bioassessment Protocol habitat index, and benthic macroinvertebrate metrics including a genus-level stream-quality index for each stream. We compared each benthic metric between impacted and unimpacted streams with a Student's t-test that incorporated adjustments for normalizing data. Impacted streams had lower genus-level stream-quality index scores; lower overall and Ephemeroptera, Plecoptera, and Trichoptera richness; fewer intolerant taxa, more tolerant taxa, and greater density of 0–3-mm individuals (P ≤ 0.10). We then used Pearson correlation to relate waterthrush metrics to benthic metrics across the 12 streams. Territory density (no. of territories/km of stream) was greater on streams with higher genus-level stream-quality index scores; greater density of all taxa and Ephemeroptera, Plecoptera, and Trichoptera taxa; and greater biomass. Clutch size was greater on streams with higher genus-level stream-quality index scores. Nest survival analyses (n = 43 nests) completed with Program MARK suggested minimal influence of benthic metrics compared with nest stage and Habitat Suitability Index score. Although our study spanned only one season, our results suggest that shale gas development affected waterthrush and benthic communities in the headwater streams we studied. Thus, these ecological effects of shale gas development warrant closer examination.