Does urbanization facilitate the establishment of introduced Monk Parakeet (Myiopsitta monachus) populations?

Date

2021-08

Authors

Johns, Nicholas E.

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Abstract

Due to increased human presence and activities, urban environments tend to facilitate the introduction and establishment of some non-native species. Because of the habitat heterogeneity, varying resources, and an overall depauperate ecological community, urban environments may provide multiple underexploited niches for colonization by novel species. The Monk Parakeet (Myiopsitta monachus) is a prime example of an introduced species that has gone through the colonization process and successfully established breeding populations in urban environments. While much of this is due to urban areas being a common point of introduction (release) for exotic species, Monk Parakeets have not spread out beyond these urban environments. My two objectives were to determine what landscape features Monk Parakeet nests might be associated with and to further our understanding of why Monk Parakeets have so far remained in urban environments, as well as identify if there were any differences in these habitat associations across the United States. I used tree canopy cover and percent impervious surface data from the 2016 National Land Cover Database GIS layers, surface water features from the National Hydrography Dataset, and observations and location data from eBird to find nest locations that were then confirmed by Google Street View. I created buffered areas around each of 280 nest locations and random points (presumed absence locations) at three different radii: 100 m, 250 m, and 500 m. I found that Monk Parakeet nests are more likely to occur in areas with low tree canopy cover and greater heterogeneity of canopy cover. This pattern of nest site habitat association appears to be roughly similar to their native range habitat, where they nested in tall trees scattered across the savanna. However, I also found that the probability of Monk Parakeet nests being present increased as the percent cover of impervious surface in the landscape increased. Even more revealing, average percent of impervious surface cover was greater around the confirmed nest sites than the absence sites, even though the absence sites were constrained to be 2 km from the nearest nest location. This shows that even within an urbanized or metropolitan area, Monk Parakeets seem to be more associated with areas that have the greatest cover of impervious surface. Availability of surface water features appeared to have very little effect on the presence of Monk Parakeets, although the data only included permanent water sources such as rivers, ponds, and lakes, not the smaller more ephemeral sources of water such as birdbaths or backyard swimming pools. I did not find a significant effect of either latitude or longitude on the relationship between any of the five environmental variables and the presence of Monk Parakeet nests, however, there was latitudinal and longitudinal-based variation in some of the five environmental variables that characterized landscapes surrounding Monk Parakeet nests. Based on the available data, the conclusions drawn from my study suggest that the establishment and growth of Monk Parakeets is facilitated by urban environments, and that they clearly rely on and have likely adapted to living in urban environments and will continue to do so into the future.

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Keywords

Monk parakeet, Introduced species, Urbanization, Urban habitat, NLCD, eBird, Nest habitat

Citation

Johns, N. E. (2021). <i>Does urbanization facilitate the establishment of introduced Monk Parakeet (Myiopsitta monachus) populations?</i> (Unpublished thesis). Texas State University, San Marcos, Texas.

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