Effect of Recreational Trails on Forest Birds: Human Presence Matters

Outdoor recreational activities are increasing worldwide and occur at high frequency especially close to cities. Forests are a natural environment often used for such activities as jogging, hiking, dog walking, mountain biking, or horse riding. The mere presence of people in forests can disturb wildlife, which may perceive humans as potential predators. Many of these activities rely on trails, which intersect an otherwise contiguous habitat and hence impact wildlife habitat. The aim of this study was to separate the effect of the change in vegetation and habitat structure through trails, from the effect of human presence using these trails, on forest bird communities. Therefore we compared the effects of recreational trails on birds in two forests frequently used by recreationists with that in two rarely visited forests. In each forest, we conducted paired point counts to investigate the differences between the avian community close (50 m) and far (120 m) from trails, while accounting for possible habitat differences, and, for imperfect detection, by applying a multi-species N-mixture model. We found that in the disturbed (i.e., high-recreation-level forests) the density of birds and species richness were both reduced at points close to trails when compared to points further away (−13 and −4% respectively), whereas such an effect was not statistically discernible in the forests with a low-recreation-level. Additionally we found indications that the effects of human presence varied depending on the traits of the species. These findings imply that the mere presence of humans can negatively affect the forest bird community along trails. Visitor guidance is an effective conservation measure to reduce the negative impacts of recreationists. In addition, prevention of trail construction in undeveloped natural habitats would reduce human access, and thus disturbance, most efficiently

Data from: Experimental evidence of human recreational disturbance effects on bird-territory establishment

The worldwide increase in human outdoor activities raises concerns for wildlife. Human disturbances, even at low levels, are likely to impact species during sensitive periods of the annual cycle. However, experimental studies during the putative sensitive period of territory establishment of birds which not only investigate low disturbance levels, but which also exclude the effect of habitat modification (e.g. walking trails) are lacking. Here, we experimentally disturbed birds in forest plots by walking through twice a day during territory establishment. Later we compared the breeding bird community of experimentally disturbed plots with that of undisturbed control plots. We discovered that the number of territories (−15.0%) and species richness (−15.2%) in disturbed plots were substantially reduced compared with control plots. Species most affected included those sensitive to human presence (assessed by flight-initiation distances), open-cup nesters and above-ground foragers. Long-distance migrants, however, were unaffected due to their arrival after experimental disturbance took place. These findings highlight how territory establishment is a sensitive period for birds, when even low levels of human recreation may be perceived as threatening, and alter settlement decisions. This can have important implications for the conservation of species, which might go unnoticed when focusing only on already established birds

Effect of human recreation on bird anti-predatory response

Wildlife perceive humans as predators, and therefore normally flushes. Flight initiation distance (FID) is the distance a human can approach an animal at a steady pace until it flushes. Recently, several studies showed differences in within-species FID according to human presence by comparing urban and rural habitats, with urban birds showing reduced FIDs. However, urban and rural habitats also differ in structure, which might affect FID. Therefore, in order to understand the real effect of human presence, we investigated whether differences in FID are also present in natural habitats (forests), differing only in the intensity of human use for recreation. We found that human frequentation had a distinct effect on bird escape responses, with shorter FIDs in forests more-heavily frequented by humans than in forests rarely visited by humans. Whether this finding is driven by non-random spatial distribution of personalities (shy vs. bold) or phenotypic plasticity (habituation to humans) cannot be assessed with our data. Studies relying on FIDs should also incorporate human recreation intensity, as this affects the measurements strongly.ISSN:2167-835

Overall number of bird territories and species as well as per nesting guild, foraging guild and sensitivity

Number of bird territories (Individuals) and bird species (Species) found in our 12 plots over the two years. Most continuous variables were scaled (mean=0, SD=1), this is indicated by (.z) at the end of the column heading "name.z".The Shannon_index refers to the tree species' which we found in our plots

Figure S1. Number of occupied split-plots per species, treatment and year.; Figure S2. Number of territories per species, treatment and year.; Figure S3. Mean number (± 95% CrI) of territories and species per split-plot according to treatment and year with the plotted corresponding posterior distribution.; Figure S4. Guild specific mean number of territories and species (± 95% CrI) according to treatment and year. Plotted are as well the corresponding posterior distributions.

Figure S1: Number of split-plots in which each species was detected at least once during the three breeding-bird censuses, separately for disturbed and control split-plots. In 2014 (a) a species could be seen in a maximum of 6 split-plots while in 2015 (b) the maximum was 12. For species abbreviations see electronic supplementary material table S1.; Figure S2: Number of territories per species for disturbed and control split-plots in the six plots of 2014 (a) and in the 12 plots of 2015 (b). For each year, the maximum number of territories per species detected in each split-plot out of the three censuses was taken and summed over all split-plots. For species abbreviations see electronic supplementary material table S1.; Figure S3: Effect of experimental human disturbance on the number of territories (a,b) and species richness (c,d) per split-plot (4.7 ha) according to year and migration type: the graphs (a) and (c) include only the resident and short-distance migrant species, while the graphs (b) and (d) only the long-distance migrants. Note the different y-axes. Represented are mean fitted values with 95% credible intervals (table 1) as well as the corresponding posterior distributions. The posterior probability (PP) shows the strength of the difference between disturbed and control split-plots.; Figure S4: Effect of experimental human disturbance on the number of territories and species richness per split-plot (4.7 ha) according to (a) nesting-guild (cavity, ground and open-cup nesters), (b) sensitivity (based on flight initiation distance (FID); high = FID > median FID, low = FID ≤ median FID), and (c) foraging guild (ground and above ground) in 2014 and 2015, respectively (only for resident and short distance migrants). Represented are mean fitted values with 95% credible intervals (Electronic supplementary material table S2-S4) as well as the corresponding posterior distributions and the posterior probability (PP) that the differences between disturbed and control split-plots are different from zero

Table S1. Bird species names (scientific, English and abbreviations) with corresponding date thresholds, classification into migration type, nesting guild, sensitivity and foraging guild. Table S2. GLMM output of the nesting guild-specific analysis. Table S3. GLMM output of the disturbance sensitivity analysis. Table S4. GLMM output of the foraging guild-specific analysis. from Experimental evidence of human recreational disturbance effects on bird-territory establishment

Table S1. Bird species recorded during the breeding bird censuses in 2014 and 2015 (n = 34), with their scientific and English names, as well as the abbreviations used for the figures (Electronic supplementary material figure S1 and S2). We also added the threshold dates after which a species was considered as a breeding bird and not a migrant passing through (according to [37]), and the classification into migration type (long-distance migrants versus others (residents and short-distance migrants)), nesting guild (cavity, ground and open-cup nesters), foraging guild (ground, above ground) and sensitivity according to flight initiation distance (FID); FID > median FID = high sensitivity, FID ≤ median FID = low sensitivity. Table S2. Results of the GLMMs testing the effect of experimental disturbance on the number of territories and species richness according to their nesting guild (Long-distance migrants were not included in these analyses, see electronic supplementary material table S1). Represented are the estimates of the effect of each variable with its corresponding 95% credible intervals (CrI). Table S3: Results of the GLMMs testing the effect of the experimental disturbance on the number of territories and species richness according to their sensitivity towards humans according to flight initiation distances (only resident and short-distance migrants were included in these analyses, see electronic supplementary material table S1). Represented are the estimates of the effect of each variable with its corresponding 95% credible intervals (CrI). Table S4: Results of the GLMMs testing the effect of experimental disturbance on the number of territories and species richness according to their foraging guild (only resident and short-distance migrants were included in these analyses, see electronic supplementary material table S1). Represented are the estimates of the effect of each variable with its corresponding 95% credible intervals (CrI)

Happy to breed in the city? : Urban food resources limit reproductive output in Western Jackdaws

Urban areas expand worldwide, transforming landscapes and creating new challenging habitats. Some bird species, mainly omnivorous feeding on human waste and cavity nesters, commonly breed in these habitats and are, therefore, regarded as urban-adapted. Although urban areas may provide new nesting sites and abundant human waste, the low breeding success found in some of these species suggests that the poor protein content in human waste might limit breeding parameters. We investigated whether the breeding success of a cavity nester and omnivorous species commonly breeding in urban areas, the Western Jackdaw (Corvus monedula), depended on the availability of good-quality non-urban food. We approached the objective by combining a literature review and experiments in the field. With the literature review, we compared jackdaw populations in different habitats across Europe and found that clutch size and number of fledglings per pair decreased with distance to non-urban foraging grounds, even after controlling for the effect of colony size, latitude, and climate. In two experiments, we tested whether the breeding success of urban pairs could be increased by supplementing high-quality food, first only during egg formation and second also until chick fledging. Food supplementation during egg formation led to larger eggs and higher hatching success than in urban control nests, but this did not result in higher chick survival. However, when food supplementation was prolonged until fledging in the second experiment, we observed a significant increase of nestling survival. These findings highlight that research and management actions should not only focus on species displaced by urbanization, but also on "urban-adapted" species, as they might be suffering from a mismatch between availability of nesting sites in buildings and adequate non-urban food resources. In these cases, nest sites should be provided in or close to adequate food resources.publishe