Bird functional diversity enhances insectivory at forest edges: a transcontinental experiment

Abstract

Aim The role of bird–insect interactions in shaping bird distribution patterns at the landscape scale has been seldom investigated. In mosaic landscapes, bird functional diversity is considered to be an important driver of avian insectivory, but depends on forest fragmentation and edge effects from adjacent, non‐forest habitats. In a transcontinental experiment, we investigated edge and landscape effects on bird functional diversity and insectivory in mosaic landscapes of mixed forests and open habitats. Location New Zealand and France. Methods We paired edge and interior plots in native forest fragments in New Zealand and native plantation forests in France. We sampled bird communities using point‐counts and linear transects respectively and simultaneously quantified avian insectivory as the rate of bird attacks on plasticine models mimicking tree‐feeding Lepidoptera larvae. The same seven life traits and attributes were compiled for French and New Zealand birds, including biogeographic origin, body mass, mobility, foraging method, adult diet, nest location and clutch size. Bird functional diversity was quantified on this multitrait basis by four indices: functional richness, evenness, divergence and dispersion. We used mixed models to test for the effects of forest edges, study area, surrounding landscape diversity and native forest cover on bird functional diversity and insectivory. Results We found higher bird functional richness at forest edges than interiors in New Zealand and lower functional richness at edges in France. However, bird functional evenness and divergence were significantly higher at forest edges in the two countries. Functional evenness and dispersion both increased with landscape diversity and evenness increased with native forest cover. Moreover, bird insectivory increased at forest edges with functional evenness, irrespective of the study area. Main conclusions We suggest that intermediate levels of forest fragmentation and edge effects increase avian insectivory in mosaic landscapes, through enhanced functional evenness and trait complementation within predatory bird assemblages.

Ecosystem Services from Small Forest Patches in Agricultural Landscapes

“…The sensitivity of biodiversity components to remnant habitat size and habitat structural quality varies significantly [41][42][43]. Sessile and less mobile organisms are more threatened by habitat degradation [40,[44][45][46] in comparison to species with good dispersal or mobility [47, 48•].…”

Effects of forest edge on pest control service provided by birds in fragmented temperate forests

“…In the selected forest stands, four transects were laid out parallel to the edge with a total length of 100 m. The distances of transects from the forest edge was the following: 0 m, 10 m, 25 m and 50 m. The distance of 50 m from immediate edge was considered as forest interior based on former studies on edge effect on caterpillar predation (Barbaro et al , 2014. The 100 m transects were used for bird survey.…”

“…Forest edges are usually characterized by diverse, bushy vegetation and thereby offer nesting and hiding places for forest birds (Saarikivi & Herczeg 2014), moreover, are expected to increase the abundance of herbivorous insects (Barber & Marquis 2011) and thereby further attract insectivorous birds (McCollin 1998). These changes in abundance both of birds and herbivores may result in increased intensity of avian insectivory (González-GÓmez et al 2006, Barbaro et al 2014. However, forest edges have been shown to also increase nest predation risk and parasitism rates which can have a strong negative effect on bird population densities (Robinson et al 1995, Batáry & Báldi 2004 and thereby can lead to decreased bird abundance at edges compared to forest interiors (Karanth et al 2006).…”

Assessment of Bird Species in Central Mindanao University, Bukidnon, Philippines

“…These birds are likely associated to their food items, like Pacific Swallows (H. tahitica) is closely associated to abundance of insect prey (Turner, 1983). The role of bird-insect interaction would depend on forest fragmentation, edge effects from adjacent non-forest habitats (Barbaro et al, 2014) and weather (Turner, 1983 (Turner, 1983). The birds belonging to family Nectariinidae, the Olive-backed Sunbird (N. jugularis) also found perching in flowering trees in open and closed canopies said to feeding on not only nectars of the flowering plants but also in small arthropods (Maher, 1996).…”

“…In agro ecosystems, the population of avian pollinators and seed dispersers during the flowering and fruiting seasons of plants and slowly declines in proportion in off season. Bird distribution patterns would also depend on the type for available food item within the area, but it depends on the forest fragment and edge pattern effects from adjacent, non-forest habitats (Barbaro et al, 2014). This study aimed to determine the bird species and its diversity in the area surrounded with a forest fragment and agro ecosystems.…”