16 Articles from The Condor, The Condor: Ornithological Applications, The Auk, The Auk: Ornithological Advances

Assessing the Impact of Invasive Species on Avian Populations: Recent Ornithological Advances in Functional and Applied Invasion Biology

By Robert J. Pecchia and Mark E. Hauber
Department of Psychology, Hunter College, and the Graduate Center, The City University of New York

Nearly 60 years after Charles Elton's (1958) The Ecology of Invasions by Animals and Plants advanced the field of invasion biology, the discipline remains the focus of many ecological and behavioral studies. The past century has witnessed the waning of so-called 'Acclimatization Societies,' responsible for both mass failed and successful introductions worldwide; instead, recent invasions are shaped by accelerating global change and increased connectivity.

In this Joint Special Collection, we selected recent publications (2013–2015) from the The Condor, The Condor: Ornithological Applications, The Auk, and The Auk: Ornithological Advances that clarify the functional underpinnings and elucidate conservation implications of invasion biology. As these works indicate, the field is well-situated to test behavioral mechanisms and genetic consequences of the invasion process and prioritize control and restoration efforts.

Applied Invasion Biology

We begin with a look at several ecosystems that have experienced anthropogenic habitat modification, a major contributor to the spread of invasive species. As North American grasslands become increasingly altered by human activity, avian communities change in response to these developments. Here we present two studies focused on populations of Greater Sage-Grouse (Centrocercus urophasianus). Accordingly, declines in Sage-Grouse abundance may be associated with Common Raven (Corvus corax) range expansion. Howe et al. (2014) determined that ravens more often nested in fragmented habitat composed of both native sagebrush (Artemisia tridentata) and invasive cheatgrass (Bromus tectorum). Increased wildfire in this landscape furthered the spread of invasive grasses, and led to fewer contiguous tracts of native vegetation. Suitable habitat for Greater Sage-Grouse has become limited, and Schulwitz et al. (2014) used molecular analysis to identify genetic connectivity between spatially isolated populations in northwest Wyoming, USA (Figure 1). Groups that now appear secluded may have had greater exchanges in the past, suggesting that cheatgrass stands and increasing development impede connectivity between regions.

Figure 1. Distribution of present and historical Greater Sage-Grouse populations in northwest Wyoming. Genetic analysis suggests that populations have become more isolated with the spread of invasive cheatgrass, and increased anthropogenic development. See Schulwitz et al. (2014).

At natural-resource extraction sites in Alberta, Canada, Ludlow et al. (2015) showed that the endemic Sprague's Pipit (Anthus spragueii) experienced decreased nestling survival as invasive wheatgrass (Agropyron cristatum) cover increased. Although modern habitat restoration projects reseed with native species, previous efforts used wheatgrass, and these sites now serve as source populations for the invasive grass. Rather than reseeding with native grasses, some management practices focus on removing nonnative vegetation. Through extensive point counts, Thompson et al. (2014) concluded that a reduction in nonnative vegetation could more than double native populations of Bobolinks (Dolichonyx oryzivorus), Sedge Wrens (Cistothorus platensis), and Savannah Sparrows (Passerculus sandwichensis) in Minnesota. Grassland development and livestock grazing has also resulted in decreased grass height and native vegetation cover in northern Mexico. In an effort to hinder declines in grassland bird abundance, Macias-Duarte and Panjabi (2013) stressed managing livestock grazing patterns, particularly in Vesper Sparrow (Pooecetes gramineus) wintering habitat, as critical for maintaining viable populations.

Much invasion biology research is conducted on islands with populations of native species that may be at risk from competitively superior nonnatives. Santa Cruz Island off the coast of California, USA, is home to the endemic Island Scrub-Jay (Aphelocoma insularis). Caldwell et al. (2013) determined that predation was associated with 92% of jay nest failures, and that increased vegetation cover may improve nestling daily survival rates. Efforts to remove nonnative herbivores (e.g., goats, sheep, pigs, and cattle) would allow native chaparral vegetation to return and may generate protected nesting sites for jays (but see Mason et al. 2014 regarding implications for other native birds). On Hawaii, VanderWerf et al. (2014) assessed survival of wild and captive-bred Puaiohi (Myadestes palmeri), a critically endangered passerine. Female Puaiohi experienced significantly greater mortality than males, which implicated high predation by invasive rats while females brood nestlings. VanderWerf et al. (2014) suggested new measures to control rats as the most effective strategy for increasing Puaiohi populations.

Contrary to conventional patterns described by invasion ecology research, recovering populations of threatened Hawaiian Geese (Branta sandvicensis) rely on exotic grasses and are found more often in anthropogenically modified habitat during breeding and molting (Leopold and Hess 2013). These authors cautioned against widespread native grass restoration within goose-breeding territories. In parallel, in the Midwest, Schneider and Miller (2014) found that the impact of invasive vegetation varied by guild. Native birds nesting in shrubs increased in abundance when associated with nonnative vegetation, whereas aerial salliers and ground-nesting birds decreased in abundance. Thus, the authors suggested thinning, rather than broad exclusion of invasive understory vegetation, as providing the greatest benefit to avian communities. In Oregon, Dinsmore et al. (2014) determined that removal of exotic grasses and addition of nesting material (e.g., shell fragments) doubled nest success for Western Snowy Plovers (Charadrius nivosus nivosus). After analyzing data on 1,900 nesting attempts over 20 years, researchers recommended limiting the use of exclosures to protect nests, and instead recommended focusing on predator removal and habitat management.

Functional Invasion Biology

We also highlight recent basic research at the intersection of functional biology and invasion ecology—these studies provide critical insight into the mechanisms facilitating invasion across a range of taxa and ecosystems. Monk Parakeets (Myiopsitta monachus) have been widely introduced to temperate regions around the world. Hobson et al. (2014) analyzed dominance hierarchies and information-sharing behaviors in wild and captive groups of Monk Parakeets. The researchers found a moderate linear hierarchy between group networks, and a surprising lack of information-sharing about novel food sources. Shealer (2014) assessed ecosystem-level foraging networks of marsh-nesting Forster's Terns (Sterna forsteri) in Wisconsin. He predicted the terns would face food limitations, citing recent habitat degradation and invasive species introductions. Through food supplementation experiments, Shealer (2014) determined that reproduction in this population was not limited by food availability.

As above, again on the Channel Islands, genetic analysis by Mason et al. (2014) indicated that endemic Horned Larks (Eremophila alpestris insularis) appear polyphyletic because they exchange individuals with mainland groups and are still experiencing lineage sorting. Introduced goats have foraged on island vegetation for the last century, improving habitat for nesting larks. Recent efforts to eradicate introduced herbivores may drive increased migration to the mainland. Ausprey and Rodewald (2013) suggested that nonnative amur honeysuckle (Lonicera maackii) had varying impacts on the spatial ecology of native species. They radio-tracked Northern Cardinals (Cardinalis cardinalis) and Acadian Flycatchers (Empidonax virescens) in habitat patches with different degrees of honeysuckle cover. The authors concluded that the presence of invasive plants had species-specific impacts on fledgling movement ecology: cardinals moved less in areas dominated by honeysuckle, while flycatchers dispersed to access more open understory.

Managed reintroductions provide an opportunity to elucidate functional underpinnings of behavior during range expansion. European rabbits (Oryctolagus cuniculus) were introduced to Laysan Island, Hawaii, USA, in the early 1900s, nearly driving the Laysan Duck (Anas laysanensis) to extinction. During recent reintroduction of the Laysan Duck to other Hawaiian Islands (part of their historical range), Walters and Reynolds (2013) observed that the Laysan Ducks may be demonstrating phenotypic plasticity remaining from the times when they occupied this larger range. The Laysan Ducks bred earlier, laid larger clutches, and renested more often. As native populations shift after invasive extirpation, it is critical that researchers monitor population dynamics. Finally, Buxton et al. (2013) assessed recovery of several species of nocturnal seabirds on the remote Aleutian Islands, Alaska, USA, following decades of introduced fox and rat removal, through innovative technology: these researchers used automatic remote acoustic recording devices and suggested that bird calls may be used as a proxy for abundance in areas that are difficult and costly to access.

Conclusion

Freile et al. (2014) cited vastly improved electronic databases and niche modeling methods as major contributors to advances in Neotropical research. They highlighted the importance of both developments in predicting invasive species impact and their distribution within ecosystems. As we outlined in this Joint Special Collection, invasion biology research has important conservation implications for broad taxonomic groups, and also provides critical insight into the functional ecology of both introduced species and native populations.

We hope this collection of recent progress in functional and applied invasion biology provides a summary of innovative work in a variety of systems. In addition, we encourage you to consider contributing future work on invasion biology to The Auk: Ornithological Advances and The Condor: Ornithological Applications to reach broad and interested audiences with your latest research.

Invasive Species Collection Articles

Selections on Applied Invasion Biology

Selection of anthropogenic features and vegetation characteristics by nesting Common Ravens in the sagebrush ecosystem by Kristy B. Howe, Peter S. Coates, and David J. Delehanty. The Condor: Ornithological Applications 116(1):35–49. Published January 2, 2014.

Low neutral genetic diversity in isolated Greater Sage-Grouse (Centrocercus urophasianus) populations in northwest Wyoming by Sarah Schulwitz, Bryan Bedrosian, and Jeff A. Johnson. The Condor: Ornithological Applications 116(4):560–573. Published October 15, 2014.

Oil and natural gas development has mixed effects on the density and reproductive success of grassland songbirds by Sarah M. Ludlow, R. Mark Brigham, and Stephen K. Davis. The Condor: Ornithological Applications 117(1): 64–75. Published January 21, 2015.

A multiscale assessment of tree avoidance by prairie birds by Sarah J. Thompson, Todd W. Arnold, and Courtney L. Amundson. The Condor: Ornithological Applications 116(3):303–315. Published May 14, 2014.

Association of habitat characteristics with winter survival of a declining grassland bird in Chihuahuan Desert grasslands of Mexico by Alberto Macías-Duarte and Arvind O. Panjabi. The Auk 130(1):141–149. Published January 2013. OPEN ACCESS

Reproductive ecology of the Island Scrub-Jay by Luke Caldwell, Victoria J. Bakker, T. Scott Sillett, Michelle A. Desrosiers, Scott A. Morrison, and Lisa M. Angeloni. The Condor 115(3):603–613. Published August 2013.

Survival estimates of wild and captive-bred released Puaiohi, an endangered Hawaiian thrush by Eric A. VanderWerf, Lisa H. Crampton, Julia S. Diegmann, Carter T. Atkinson, and David L. Leonard. The Condor: Ornithological Applications 116(4):609–618. Published November 5, 2014. OPEN ACCESS

Multi-scale habitat selection of the endangered Hawaiian Goose by Christina R. Leopold and Steven C. Hess. The Condor 115(1):17–27. Published February 2013. OPEN ACCESS

Response of avian communities to invasive vegetation in urban forest fragments by Sarah C. Schneider and James R. Miller. The Condor: Ornithological Applications 116(3):459–471. Published July 23, 2014.

Predator exclosures, predator removal, and habitat improvement increase nest success of Snowy Plovers in Oregon, USA by Stephen J. Dinsmore, David J. Lauten, Kathleen A. Castelein, Eleanor P. Gaines, and Mark A. Stern. The Condor: Ornithological Applications 116(4):619–628. Published November 5, 2014.

Selections on Functional Invasion Biology

The socioecology of Monk Parakeets: Insights into parrot social complexity by Elizabeth A. Hobson, Michael L. Avery, and Timothy F. Wright. The Auk: Ornithological Advances 131(4): 756–775. Published September 17, 2014. OPEN ACCESS

No evidence of food limitation during the breeding season of a freshwater marsh-nesting tern by David A. Shealer. The Auk: Ornithological Advances 131(3):378–387. Published July 2, 2014.

Genetic variation among western populations of the Horned Lark (Eremophila alpestris) indicates recent colonization of the Channel Islands off southern California, mainland-bound dispersal, and postglacial range shifts by Nicholas A. Mason, Pascal O. Title, Carla Cicero, Kevin J. Burns, and Rauri C. K. Bowie. The Auk: Ornithological Advances 131(2):162–174. Published March 5, 2014.

Post-fledging dispersal timing and natal range size of two songbird species in an urbanizing landscape by Ian J. Ausprey and Amanda D. Rodewald. The Condor 115(1):102–114. Published February 2013. OPEN ACCESS

Experimental reintroduction reveals novel life-history variation in Laysan Ducks (Anas laysanensis) by Jeffrey R. Walters and Michelle H. Reynolds. The Auk 130(4):573–579. Published October 2013. OPEN ACCESS

Examining patterns in nocturnal seabird activity and recovery across the Western Aleutian Islands, Alaska, using automated acoustic recording by Rachel T. Buxton, Heather L. Major, Ian L. Jones, and Jeffrey C. Williams. The Auk 130(2):331–341. Published April 2013. OPEN ACCESS

Current Neotropical ornithology: Research progress 1996–2011 by Juan F. Freile, Harold F. Greeney, and Elisa Conaccorso. The Condor 116(1):84–96. Published January 2014. OPEN ACCESS