Space invaders: House Sparrow densities along three urban-agricultural landscapes

Abstract

ABSTRACT. One of the most successful avian urban invaders is the House Sparrow (Passer domesticus). Here, we examine House Sparrow numbers in the urban-agricultural landscape of three cities, one where the sparrow is native (Barcelona) and two where it is nonnative (Los Angeles, Mexico City), comparing between five different land classes based on land-use, location relative to urban center, and urbanization intensity. We estimated sparrow densities using distance-sampling corrected procedures and compared sparrow numbers between the three cities and between the land classes within each city. This two-year survey showed the highest density of sparrows occurring in Mexico City and the lowest in Los Angeles. In both cities where the sparrow is nonnative, we recorded the greatest abundances in highly urbanized areas. In Barcelona, where the sparrow is native, abundances did not differ among land classes. We also related sparrow numbers to specific environmental variables, describing vegetation structure, urban infrastructure, and human activity, using classification and regression trees. We found several variables related to differences in House Sparrow abundances among the three cities. For Los Angeles and Mexico City, the most important variables explaining House Sparrow numbers were urban infrastructure (i.e., maximum building height, high urbanization) and/or human activity (i.e., pedestrians), all of which related positively with sparrow abundance. For Barcelona, sparrow numbers showed both positive and negative relationships with vegetation (i.e., tree abundance, maximum tree height, maximum herbaceous plant height) and human-related variables (i.e., cars, pedestrians). Although the scope of this study is geographically limited to three cities, our results suggest that House Sparrow numbers between cities and land classes areas vary considerably, and are likely determined by a complex array of variables. Our study provides some insight to the growth and decline of House Sparrow populations in their nonnative and native ranges, respectively. Alerte aux envahisseurs: Densités de moineaux domestiques au long de trois paysages agrico-urbainsRÉSUMÉ. Un des envahisseurs aviaires ayant le plus de succès est le Moineau Domestique (Passer domesticus). Ici, nous examinons les densités dans les zones agrico-urbaines de trois villes, une où le moineau est natif (Barcelone) et deux où l'espèce est considérée envahissante (Los Angeles, Mexico), en comparant entre cinq classifications terrestres établit selon l'utilisation du territoire, localisation relative au centre urbain, et l'intensité d'urbanisation. Nous avons estimé les densités de moineaux en utilisant la méthode d'échantillonnage selon la distance corrigée et avons comparé le nombre de moineau entre les trois villes, ainsi qu'entre les classifications terrestres dans chaque ville. Cet échantillonnage de deux ans a démontré la plus grande densité à Mexico et la plus basse à Los Angeles. Chez les deux villes où le moineau est considéré comme envahissant, les densité...

On the lookout for danger: House Sparrow alert distance in three cities

“…Given that alert distances were significantly higher in Barcelona when compared to those from Mexico City and Los Angeles, our findings support our first hypothesis (relation between House Sparrow invasiveness and boldness). Yet, due to the fact that alert distances were significantly lower in Mexico City when contrasted to those recorded at Los Angeles, our results are also in agreement with our second prediction, showing a positive association between alert distances and House sparrow densities, at least in cities where it is non-native and invasive (see MacGregor-Fors et al 2017).…”

“…Nevertheless, our results clearly show that House Sparrow alert distances in one city located within the region where we consider it native (i.e., Barcelona) were significantly larger when compared to both studied North American cities. Given that alert distances were significantly larger in Los Angeles when contrasted with those from Mexico City (where it is hyper-abundant; MacGregor-Fors et al 2017), our results also suggest that its boldness could be related to density-dependent processes. Based on our results and others in the literature, we suggest that future studies could add evidence to or refute this phenomenon by including a wider array of cities, testing hypotheses related to the familiarization to humans, geographical variations, as well as the physiology of House Sparrows, and including scenarios in which House Sparrows are hyper-abundant, as well as scarce, and finding strategies to sex and age all of the assessed individuals.…”

“…Yet, there is an important dearth of knowledge on the behavior of this species, essentially circumscribed to urban-agricultural landscapes throughout its North American invasion distribution. Recently, a study focused on House Sparrow densities in three urban-agricultural landscapes related to three cities (i.e., Barcelona, Los Angeles, Mexico City) showed differing results among and within landscapes (MacGregor-Fors et al 2017). Briefly, this study reports higher densities in the studied landscape including Mexico City and lower densities in those of Los Angeles and Barcelona, showing that their densities are not dependent from the origin of their populations (i.e., native, exotic).…”

“…We had two mutually exclusive predictions related to a behavioral response (i.e., alert distances) of House Sparrow and their population densities: (1) if their invasiveness is related with their boldness, we then predicted individuals from Los Angeles and Mexico City (which are part of the North American invasion population) to be less wary about human approaches than those from Barcelona (which is part of the distribution range considered to be native for the species), resulting in shorter alert distances in these two cities, and (2) if their densities are related to their boldness, we then expected individuals in the city where higher densities were recorded (i.e., Mexico City: average density during the breeding season: 11.6-21.7 ind/ha; MacGregor-Fors et al 2017) to be less wary about human approaches than those from lower density cities (i.e., Barcelona: average density during the breeding season: 4.5-5.7 ind/ha; Los Angeles: average density during the breeding season: 1.2-2.5 ind/ha; MacGregor-Fors et al 2017), resulting in shorter alert distances in Mexico City when compared with Barcelona and Los Angeles.…”

Bird Community Assemblage and Distribution in a Tropical, Urban Ecosystem of Puerto Rico

“…We documented many endemic resident species (e.g., Adelaide's Warbler [Setophaga adelaidae]), resident species (e.g., Bananaquit), and neotropical migrants (e.g., Hooded Warbler [Setophaga citrina]) across the installation. While on average, cities may support more native species than exotics (Aronson et al, 2014), urban areas often host high densities of exotics such as House Sparrows (Passer domesticus; MacGregor-Fors, Quesada, Lee, & Yeh, 2017) and Rock Pigeons (Columba livia; Beissinger & Osborne, 1982;Greene, 1984). While both species occurred on Fort Buchanan, they were in limited numbers and primary found near commercial and urbanized areas of the installation.…”