Arthropod Communities Associated with Habitats Occupied by Breeding Swainson's Warblers

Abstract

The Swainson's Warbler (Limnothlypis swainsonii) is an insectivorous songbird and a species of conservation concern in the southeastern U.S. Because it is specialized for foraging in the litter of the forest floor, it is dependent on a well-developed leaf-litter layer. However, this reliance on the litter layer likely reflects selection of habitats with abundant arthropods for food. To investigate this possibility, we examined relationships between Swainson's Warbler presence and both abundance and diversity of ground-dwelling and litter arthropods. In 2004 and 2005, using song playbacks, we surveyed 1453 sites and collected arthropods in litter samples and pitfall traps at 45 randomly selected occupied and unoccupied sites. In litter samples, total mean arthropod abundance, abundance of arthropods >5 mm in length, total abundance of adults, and taxonomic richness were significantly greater at sites occupied by Swainson's Warblers than at unoccupied sites. In pitfall data, however, we detected no differences between occupied and unoccupied sites. Additionally, the abundance of several taxa known to be Swainson's Warbler food, most notably beetles, was greater at occupied than at unoccupied sites. Overall, the taxonomic richness and abundance of large arthropods were the best predictors of Swainson's Warbler presence. These results suggest that arthropod abundance and taxonomic richness are key habitat components for Swainson's Warbler. Because the arthropod community may be a driving factor influencing the presence of Swainson's Warbler, management that maintains or improves the leaf-litter layer and promotes ground-and litter-dwelling arthropods will be beneficial for managing habitats for this and other ground-foraging species. Comunidades de Artrópodos Asociadas con Habitats Ocupados por Individuos Reproductivos deLimnothlypis swainsoniiResumen. Limnothlypis .swainsonii es una especie de ave insectívora con estatus de conservación preocupante en el sudeste de EEUU. Debido a que se especializa en forrajear en la hojarasca del suelo del bosque, depende de sitios con capas de hojarasca bien desarrolladas. Sin embargo, esta dependencia de capas de hojarasca refleja probablemente una selección de habitats con gran cantidad de artrópodos para alimento. Para investigar esta posibilidad, examinamos la relación entre la presencia de L. swainsonii y la abundancia y diversidad de artrópodos terrestres de la hojarasca. En 2004 y 2005, emitiendo reproducciones de cantos para atraer a las aves, muestreamos 1453 sitios y colectamos artrópodos en muestras de hojarasca y en trampas de caida en 45 sitios seleccionadas al azar ocupados y desocupados. En las muestras de hojarasca, la abundancia promedio de artrópodos total, la abundancia de artrópodos >5 mm de largo, la abundancia total de adultos y la riqueza taxonómica fueron significativamente mayores en los sitios ocupados por L. swainsonii que en los sitios desocupados. Además, la abundancia de varios taxones de artrópodos que se conoce que son alimento para L. swainsonii, p...

Recent large-scale colonisation of southern pine plantations by Swainson’s WarblerLimnothlypis swainsonii

“…As previously mentioned, the warbler forages almost exclusively in terrestrial dead-leaf litter (Meanley 1970, Graves 1998). Although their foraging behaviour in pine plantations is unknown, published data from broadleaf habitats (Graves 1998, Brown et al 2011) suggest that deciduous leaf litter is an integral component of breeding territories. It remains to be determined whether this is true for territories in pine plantations.…”

“…Henry ( 2004 ) and Legrand et al ( 2007 ) found the warbler to be a predictable breeder in pine plantations in the same area during 2002. My recent surveys (2007-2011 documented breeding territories in pine plantations in 21 parishes in Louisiana distributed throughout the pine-dominated regions of the state ( Figure 1 ).…”

“…Swainson's Warbler is a terrestrial dead-leaf specialist (Meanley 1970, Graves, 1998 ) that feeds on litter arthropods (Savage et al 2010, Brown et al 2011. The distribution of soils is believed to be an important determinant of local and regional patterns of habitat selection in Swainson's Warbler (Graves 1998(Graves , 2001(Graves , 2002, to the extent that soil type and moisture influence the accumulation and decay of leaf litter and the taxonomic diversity and abundance of litter arthropods.…”

Effects of prescribed burning on swainson's warbler home‐range size and habitat use

“…The direct effects of management on leaf-litter arthropods have shown increases (Harris and Whitcomb 1974), decreases (Anderson et al 1989, Coleman and Rieske 2006, Ferrenberg et al 2006, or little effect (Greenberg et al 2010). Brown et al (2011) suggested that arthropods may be the driving factor in habitat selection for Swainson's warblers, whereas leaf litter may be a proximate cue. Slight changes in habitat conditions may have a large impact on the arthropod communities that this species depends upon.…”

Catastrophic storms, forest disturbance, and the natural history of Swainson's warbler

“…Habitat suitability is also influenced by flooding (Graves, 2001 ; Reiley, 2012 ), soil type, and soil moisture levels (Graves, 2002 , 2015 ). These factors affect the deposition and decay of leaf litter and abundance and diversity of terrestrial litter arthropods (Brown, Benson, & Bednarz, 2011 ; Savage et al., 2010 ), which are essential resources for this dead‐leaf foraging specialist (Graves, 1998 ). The entire breeding distribution is characterized by moderate annual precipitation, and only a few peripheral breeding sites in Texas lie outside the 1000 mm‐isohyet.…”