Response Of Bird Communities Research Articles

Comparison of bird community indices for riparian restoration planning and monitoring

The use of a bird community index that characterizes ecosystem integrity is very attractive to conservation planners and habitat managers, particularly in the absence of any single focal species. In riparian areas of the western USA, several attempts at arriving at a community index signifying a functioning riparian bird community have been made previously, mostly resorting to expert opinions or national conservation rankings for species weights. Because extensive local and regional bird monitoring data were available for Nevada, we were able to develop three different indices that were derived empirically, rather than from expert opinion. We formally examined the use of three species weighting schemes in comparison with simple species richness, using different definitions of riparian species assemblage size, for the purpose of predicting community response to changes in vegetation structure from riparian restoration. For the three indices, species were weighted according to the following criteria: (1) the degree of riparian habitat specialization based on regional data, (2) the relative conservation ranking of landbird species, and (3) the degree to which a species is under-represented compared to the regional species pool for riparian areas. To evaluate the usefulness of these indices for habitat restoration planning and monitoring, we modeled them using habitat variables that are expected to respond to riparian restoration efforts, using data from 64 sampling sites in the Walker River Basin in Nevada and California. We found that none of the species-weighting schemes performed any better as an index for evaluating overall habitat condition than using species richness alone as a community index. Based on our findings, the use of a fairly complete list of 30–35 riparian specialists appears to be the best indicator group for predicting the response of bird communities to the restoration of riparian vegetation.

Effects of time since fire on birds in a plant diversity hotspot

Global changes are influencing fire regimes in many parts of the world. In the Fynbos plant diversity hotspot (Cape Floristic Region, South Africa), fire frequency has increased in protected areas where the mean fire interval went from 12–19 to 6–9 years between 1970 and 2000. Fire is one of the main drivers of plant diversity in the Cape Floristic Region. Too frequent fires threaten the persistence of slow-maturing plant species, and such insights have led to the adoption of fire management principles based on plant responses. The effects of fire on Fynbos fauna are much more poorly understood, and have not generally been considered in depth in Fynbos conservation policies, planning or management. We assessed the response of bird communities to long-term fire-induced vegetation changes using space-for-time substitution. We studied bird communities, vegetation structure and plant functional composition in 84 Fynbos plots burnt between two and 18 years before. Ten of the 14 bird species analysed showed a significant change in their abundance with time since fire. We observed a significant species turnover along the post-fire succession due to changes both in vegetation structure and plant functional composition, with a characteristic shift from non-Fynbos specialists and granivorous species to Fynbos specialists and nectarivorous species.If current trends of increasing fire frequency continue, Fynbos endemic birds such as nectarivores may become vulnerable. Conservation management should thus aim more carefully to maintain mosaics of Fynbos patches of different ages. Future research needs to estimate the proportion of vegetation of different ages and patch sizes needed to support dependent fauna, particularly endemics.

Assessing the short-term effects of an extreme storm on Mediterranean forest raptors

Different species show different responses to natural disturbances, depending on their capacity to exploit the altered environment and occupy new niches. In the case of semi-arid Mediterranean areas, there is no information available on the response of bird communities to disturbance caused by extreme weather events. Here, we evaluate the short-term effects of a heavy snowfall and strong winds on three long-lived species of forest-dwelling raptor in a semi-arid Mediterranean region situated in the south-east of Spain. The loss of nests was significantly higher in the first and second years following the disturbance than in the third year. The three species studied exhibited great tolerance to the short-term effects of the storm since we found no differences in density or reproductive parameters between the nine breeding seasons prior to the disturbance and the three which immediately followed it. We suggest that the tolerance shown by these three species to windstorms in semi-arid Mediterranean zones could be an adaptive response, resulting from the climatic and human pressures which have prevailed from the Bronze Age to the present day.

Habitat loss and fragmentation affecting mammal and bird communities—The role of interspecific competition and individual space use

Fragmentation and loss of habitat are major threats to animal communities and are therefore important to conservation. Due to the complexity of the interplay of spatial effects and community processes, our mechanistic understanding of how communities respond to such landscape changes is still poor. Modelling studies have mostly focused on elucidating the principles of community response to fragmentation and habitat loss at relatively large spatial and temporal scales relevant to metacommunity dynamics. Yet, it has been shown that also small scale processes, like foraging behaviour, space use by individuals and local resource competition are also important factors. However, most studies that consider these smaller scales are designed for single species and are characterized by high model complexity. Hence, they are not easily applicable to ecological communities of interacting individuals. To fill this gap, we apply an allometric model of individual home range formation to investigate the effects of habitat loss and fragmentation on mammal and bird communities, and, in this context, to investigate the role of interspecific competition and individual space use. Results show a similar response of both taxa to habitat loss. Community composition is shifted towards higher frequency of relatively small animals. The exponent and the 95%-quantile of the individual size distribution (ISD, described as a power law distribution) of the emerging communities show threshold behaviour with decreasing habitat area. Fragmentation per se has a similar and strong effect on mammals, but not on birds. The ISDs of bird communities were insensitive to fragmentation at the small scales considered here. These patterns can be explained by competitive release taking place in interacting animal communities, with the exception of bird's buffering response to fragmentation, presumably by adjusting the size of their home ranges. These results reflect consequences of higher mobility of birds compared to mammals of the same size and the importance of considering competitive interaction, particularly for mammal communities, in response to landscape fragmentation. Our allometric approach enables scaling up from individual physiology and foraging behaviour to terrestrial communities, and disentangling the role of individual space use and interspecific competition in controlling the response of mammal and bird communities to landscape changes.

Bird community response to mid‐rotation management in conservation reserve program pine plantations

AbstractOpen pine–grasslands are one of the most threatened ecological communities in the southeastern United States and provide essential habitat for many regionally declining bird species. While open pine–grassland forests have diminished, acreage of pine plantations has increased throughout the Southeast, in part because of the U.S. Department of Agriculture Farm Bill conservation programs. To understand whether fire and herbicide treatments would be effective in creating pine–grassland structure in plantations suitable for a suite of declining early successional and pine–grassland adapted species, we evaluated combined effects of selective herbicide and prescribed fire on plant and bird communities in thinned, mid‐rotation pine stands established under the Conservation Reserve Program (CRP) in Mississippi, USA. Within each of the 12 replicate sites, we assigned 2 paired 8.1‐ha plots to either treatment (herbicide + prescribed fire) or control in a randomized complete block design. We applied treatments during autumn and winter of 2002–2003. During 2003–2006 breeding seasons, we characterized the bird community using repeated (4–6 repetitions/yr), standardized, 10‐minute point counts from which we estimated species richness, total relative abundance, total avian conservation value, and density of select species. Managed plots exhibited reduced hardwood midstory and a greater abundance of grasses and forbs in the ground layer. Although avian species richness and total relative abundance were similar in treatment and control stands, we observed a shift in the bird community from closed‐canopy forest species to early successional and pine–grassland adapted species, many of which are experiencing population declines. We recommend thinning, hardwood midstory control, and prescribed burning within CRP pine plantations to provide habitat for a suite of regionally declining bird species. © 2012 The Wildlife Society.

Contrasting spatial and temporal responses of bird communities to landscape changes

Quantifying the impact of land-use changes on biodiversity is a major challenge in conservation ecology. Static spatial relationships between bird communities and agricultural landscapes have been extensively studied. Yet, their ability to mirror the effects of temporal land-use dynamics remains to be demonstrated. Here, we test whether such space-for-time substitution approaches are relevant for explaining temporal variations in farmland bird communities. We surveyed 256 bird communities in an agricultural landscape in southwest France at the same locations in 1982 and 2007, and quantified the same seven landscape descriptors for each period. We compared the effects of spatial and temporal landscape changes over this 25-year period on bird species distributions and three community-level metrics: species richness and two community indices reflecting birds' specialisation regarding local vegetation structure (local CSI) and landscape composition (landscape CSI). Landscape heterogeneity decreased between 1982 and 2007 and crop area increased sharply at the expense of grassland as a result of agricultural intensification. We found that the correlations between temporal changes in bird distributions or community metrics and landscape components were less consistent than their spatial relationships in each year. This result advocates caution when using a space-for-time substitution approach to assess the effects of landscape changes on biodiversity. Additionally, community metrics showed contrasted responses to landscape changes. Species richness and local CSI for each period were negatively related to the area of crops and positively related to landscape heterogeneity. Conversely, the landscape CSI was positively related to the area of crop and negatively to landscape heterogeneity. To understand the ecological processes linked to changes in farm landscapes, our study underlines the need to develop long-term studies with bird and habitat data collected during several periods, and particularly to consider multiple community indices in monitoring change.

Bird community dynamics and vegetation relationships among stand establishment practices in intensively managed pine stands

Intensively managed pine occupies 22% of the forest land base in the southeastern United States. More fully understanding effects of standard silvicultural practices on biodiversity could improve wildlife management recommendations on intensively managed landscapes. Although multiple stand-establishment techniques (i.e., site preparation and chemical herbaceous control of competition) are used for forest regeneration, we lack an understanding of causal mechanisms for bird community responses during stand establishment through canopy closure. Therefore, we investigated bird community responses to five stand-establishment treatments in intensively managed pine (Pinus spp.) stands in the Lower Coastal Plain of Mississippi, USA as a function of changes in vegetation structure and coverage. We used a randomized complete block design of four pine stands (blocks) divided into five experimental units and with treatments randomly assigned to each unit. Our treatments represented available establishment practices and increased in intensity from mechanical or chemical site preparation with subsequent banded herbaceous control to mechanical and chemical site preparation with 2years of subsequent broadcast herbaceous weed control applications. We sampled bird communities with point counts and measured visual obstruction, pine tree height, woody stem density, and vegetation structure and coverage by growth form (e.g., forb, fern, grass, legume, pine, sedge and rush, woody non-pine, vine). Bird communities had an overall negative response to increasing intensity of stand-establishment treatments, and temporal trends from site preparation to canopy closure were absent. Common species appeared relatively unaffected by treatments. However, presence of species with high conservation value and availability of early successional habitat conditions emphasized conservation potential of intensively managed pine forests for birds and justify further experimental investigation of bird community responses to stand-establishment treatments. We recommend forest managers continue to incorporate a variety of stand establishment practices to ensure habitat availability for a variety of bird species, and that researchers further investigate mechanistic factors of avian community responses to silvicultural practices.

Response of bird communities to single-tree selection system harvesting in northern hardwoods: 10–12 years post-harvest

We previously investigated the responses of forest birds to habitat changes 1–7years post-harvest in three northern Ontario tolerant hardwood forest stands cut under the selection system. The same three cut blocks and a control area were re-sampled in 2009, 10–12years post-harvest, to compare community composition, total and species abundances and species richness. We found that the breeding bird communities of the selection cut blocks had not fully recovered 10–12years post-harvest. Veery, Chestnut-sided Warbler, Magnolia Warbler, American Redstart and Mourning Warbler numbers were elevated in all three cut blocks, and White-throated Sparrow numbers were elevated in two of the three cut blocks, 10–12years post-harvest. In contrast, Ovenbird numbers remained depressed in two cut blocks 10–12years post-harvest. Overall, species richness remained high in all three cut blocks, even though total abundance declined. The data suggest that repeated applications of selection cutting could have long-term, cumulative effects on forest bird communities.

Bird Community Response to Vegetation Cover and Composition in Riparian Habitats Dominated by Russian Olive (Elaeagnus angustifolia)

Riparian systems in the western United States provide important habitat for bird communities during all times of the year. In recent decades, invasive plants, such as Russian olive (Elaeagnus angustifolia), have achieved broad distribution and local dominance in many western riparian areas, raising concerns over the loss of ecological function within these systems. In 2005 and 2006 we conducted avian point counts and surveyed vegetation cover at 95 points along the Snake and Columbia Rivers in southeastern Washington to investigate the effects of total woody vegetation cover and the relative proportion of Russian olive cover on breeding and wintering riparian bird communities. Our results indicated that riparian habitats dominated by Russian olive can support diverse and abundant bird communities, though cavity nesting species were noticeably sparse. Bird density and species richness were best explained by a quadratic relationship to total woody vegetation cover in both seasons, as was breeding bird community composition, with greatest density and richness in intermediate cover levels. We found no indication that the proportion of the woody vegetation comprised of Russian olive strongly influenced any of these bird community metrics. Given that Russian olive comprised 81.6% of the riparian vegetation in our study area, it is unclear from our results how Russian olive would affect bird communities in regions where native vegetation is more abundant. Regardless, complete eradication of Russian olive from riparian systems where the plant is a major component will reduce the overall habitat value for birds by eliminating significant structural complexity.

Bird community responses to cattle stocking rates in a Pacific Northwest bunchgrass prairie

In 2006–2010, effects of four different cattle stocking rates (0, 14.4, 28.8, and 43.2 animal unit months) were compared, representing 0%, 20%, 32%, and 46% utilization of vegetation by domestic livestock, on vegetation structure (as indexed by visual obstruction), and songbird population and apparent nest density, community composition, and diversity in a Pacific Northwest bunchgrass prairie in northeastern Oregon, USA. Overall paddock-level visual obstruction decreased and structural heterogeneity increased with increasing stocking rates, and those effects carried over 1 year after grazing had ceased. Most species were able to locate nesting sites regardless of differences in visual obstruction, except western meadowlark and vesper sparrow, for which obstruction was lower in paddocks with higher stocking rates. Apparent nest density for grasshopper sparrows was negatively affected by higher stocking rates. Grazing effects on absolute songbird population density were restricted to negative effects of higher stocking rates on savannah sparrows, but this relationship was not observed until 1 year after grazing had ceased. Songbird community composition differed between control and heavily-grazed paddocks, driven by an increase in the proportion of horned larks and a decrease in the proportion of savannah sparrows in heavily-grazed paddocks from pre-treatment to post-treatment years. Bird diversity indices were unaffected by stocking rate. Negative effects of high stocking rates on densities of two species and the absence of any clear positive effect for the other three species suggest high stocking rates as applied in this experiment may not provide suitable habitat for all grassland songbirds. The absence of negative responses of density to low and moderate stocking rates suggests these grazing regimes generally provided suitable habitat for all species.

Landscape changes caused by high altitude ski-pistes affect bird species richness and distribution in the Alps

There is a paucity of research on the wider landscape-level effects of ski-piste construction on alpine fauna. In this study, the response of alpine bird communities to the landscape changes induced by the construction of ski-pistes was investigated in the western Italian Alps. The aims were: (i) to test the hypothesis that ski-pistes have a detrimental effect on alpine grassland bird communities at a landscape-scale; and, (ii) to model local probability distributions of bird species according to different scenarios of ski-piste restoration and ski-piste proliferation above the treeline. Species richness and presence/absence data from point counts were analyzed in relation to GIS-derived landscape variables based on a 16ha hexagon grid. Predictive variables were selected through the LASSO model selection procedure, and logistic regression was used to estimate the probability of occurrence of each species in each hexagon. Grassland species richness, and probability of occurrence of water pipit, wheatear and black redstart, significantly decreased with increasing extent of ski-piste edge. Length of ski-piste edge was in the set of best models considering a large range of habitat and landscape predictors, and are therefore clearly features that exert a strong negative effect on high alpine grassland bird communities. Predictions of species occurrence were made by applying the models to different scenarios of habitat change. These showed predicted detrimental impacts of a relatively small 10% increase in ski-piste extent, but also that grassland restoration on existing ski-pistes could result in significantly increased occurrence rates of alpine grassland species. This study suggests that ski-pistes are perceived by birds as detrimental features of the alpine landscape. To minimize their impact, new, environmentally–friendly ways of constructing pistes should be developed, which could include habitat restoration and management to obtain a level of grass cover such that edges of ski-pistes are no longer perceived by birds.

Bird community responses to a gradient of site preparation intensities in pine plantations in the Coastal Plain of North Carolina

Although intensively managed pine forests are common in the southeastern US, few studies describe how combinations of mechanical (MSP) and chemical site preparation (CSP) and herbaceous weed control (HWC) techniques affect bird communities that use early successional habitats within young pine forests. Therefore, we examined effects of six treatments of increasing management intensity via combinations of MSP (strip-shear and wide spacing or roller chop and narrow spacing) and CSP (application or no application) treatments with banded or broadcast HWC on bird communities in six loblolly pine ( Pinus taeda) plantations in the Coastal Plain of North Carolina, USA, for 8 years following site preparation. Wide pine spacing and strip-shear MSP increased bird abundance and species richness over narrow spacing and chopped MSP for 6 years after planting. Chemical SP reduced bird abundance in year 2, increased bird abundance in year 6, had no effect on abundance after year 7, and did not affect species richness in any year. Total bird abundance and species richness were similar between banded and broadcast HWC. Site preparation and HWC had no effect on bird diversity and bird communities were most similar in treatments of similar intensity. Site preparation and HWC had few or no effects on birds based upon migratory status, habitat association, or conservation value. The addition of chemical site preparation or HWC had little effect on birds beyond pine spacing, and bird abundance was not proportional to management intensity. Although we observed treatment effects, all treatments provided habitat used by a variety of bird species, and pine plantations may play an increasingly important role in bird conservation as forests become fragmented and converted to other land uses and as natural processes that create early successional habitat, such as fire, are suppressed.

Ten-year response of bird communities to an operational herbicide–shelterwood treatment in a northern hardwood forest

Use of herbicides in forestry to direct successional trajectories has raised concerns over possible direct or indirect effects on non-target organisms. We studied the response of forest birds to an operational application of glyphosate and sulfometuron methyl herbicides, using a randomized block design in which half of each 8 ha block received herbicide and the other acted as a control, on shelterwood seed-cut Allegheny hardwood stands in northwestern Pennsylvania. We monitored birds using 50 m radius point counts in two pretreatment years and for 10 years post-treatment (1992–2004). Fences were erected six years after herbicide treatment in response to increased deer browsing at a subset of sites. Avian responses to herbicide treatment varied by nesting guild: we detected no response by cavity-nesters, but documented declines in the shrub-, ground- and canopy-nesting guilds. Responses were short-lived (2–4 years post-treatment), but shrub-nesters did not recover until fencing provided regenerating vegetation respite from browsing. Thus, apparent responses of birds to herbicide were confounded with deer browsing in this study. High species turnover, even within control plots, suggests that avian communities may be assessed more appropriately assessed at larger spatial scales than those used in this study (6.5–8 ha).

Bird Community Responses to Vegetation Heterogeneity Following Non-Direct Regeneration of Mediterranean Forests after Fire

Zozaya E.L., Brotons L. & Vallecillo S. 2011. Bird community responses to vegetation heterogeneity following non-direct regeneration of Mediterranean forests after fire. Ardea 99: 73–84.

Bird community response to filter strips in Maryland

AbstractFilter strips are strips of herbaceous vegetation planted along agricultural field margins adjacent to streams or wetlands and are designed to intercept sediment, nutrients, and agrichemicals. Roughly 16,000 ha of filter strips have been established in Maryland through the United States Department of Agriculture's Conservation Reserve Enhancement Program. Filter strips often represent the only uncultivated herbaceous areas on farmland in Maryland and therefore may be important habitat for early‐successional bird species. Most filter strips in Maryland are planted to either native warm‐season grasses or cool‐season grasses and range in width from 10.7 m to 91.4 m. From 2004 to 2007 we studied the breeding and wintering bird communities in filter strips adjacent to wooded edges and non‐buffered field edges and the effect that grass type and width of filter strips had on bird community composition. We used 5 bird community metrics (total bird density, species richness, scrub‐shrub bird density, grassland bird density, and total avian conservation value), species‐specific densities, nest densities, and nest survival estimates to assess the habitat value of filter strips for birds. Breeding and wintering bird community metrics were greater in filter strips than in non‐buffered field edges but did not differ between cool‐season and warm‐season grass filter strips. Most breeding bird community metrics were negatively related to the percent cover of orchardgrass (Dactylis glomerata) in ≥1 yr. Breeding bird density was greater in narrow (<30 m) compared to wide (>60 m) filter strips. Our results suggest that narrow filter strips adjacent to wooded edges can provide habitat for many bird species but that wide filter strips provide better habitat for grassland birds, particularly obligate grassland species. If bird conservation is an objective, avoid planting orchardgrass in filter strips and reduce or eliminate orchardgrass from filter strips through management practices. © 2011 The Wildlife Society.

A review of the interaction between forest birds and eastern spruce budworm

The eastern spruce budworm, Choristoneura fumiferana Clem., (hereafter budworm) is responsible for the largest areas of insect-caused disturbance in North America, and as such, is an important part of spruce–fir forest change and succession. The insectivorous forest bird community shows large and rapid responses to budworm outbreaks. There is good evidence that there are budworm-linked species (bay-breasted, Cape May, and Tennessee warblers) that respond to budworm outbreak much more strongly and consistently than other species, probably through increased productivity of local populations when budworm are abundant. There also appears to be a more widespread positive bird community response to budworm outbreak that involves many more species. The response is evident in local and regional scale studies, but individual species’ responses across studies are not always consistent, probably because of the relatively small number of studies conducted in a wide variety of contexts. Budworm outbreaks provide a short-term increase in food supply for birds, but also result in longer-term habitat change due to budworm-induced defoliation and tree mortality. Birds appear to influence budworm cycles, mostly at endemic population levels, through predation of large larvae and pupae. There are good arguments suggesting that bird predation is not the primary cause of budworm oscillations, but may play a role in determining the mean level of oscillations. Climate change is expected to change the bird–budworm relationship through changes in fire regimes, spruce–fir distributions, bird distributions, and budworm and bird phenology.

Migrating to the City: Responses of Neotropical Migrant Bird Communities to Urbanization

Abstract. Birds that migrate to the neotropics have experienced dramatic population decreases over the last few decades. Although the transformation of their wintering habitats has been related to such decreases, several neotropical migrants are tolerant of human disturbances and winter in human-altered habitat. We surveyed a neotropical city broadly to evaluate how migrant birds respond to urbanization, finding that urbanization has a negative effect on communities of migrant birds: species richness and density of migrants decreased with urbanization. Although we recorded a significant decrease in the total number of individual neotropical migrants toward the center of the city, we found no differences among species when we assessed possible effects of the distance from the city's edge by species. Only tree cover had a positive significant relationship with both species richness and bird abundance. Our results show that urbanization can have an even greater negative effect on communities of neotropical m...

Agricultural land-use in the surrounding landscape affects moorland bird diversity

A multi-scale approach was used to investigate the response of the moorland bird community to agricultural land-use in the surrounding matrix and local-scale vegetation characteristics. For the assemblage of upland specialist species, there was a negative association with the extent of intensively managed grassland at the 750m spatial scale. This had a greater influence on richness than the local vegetation characteristic of the moorland itself. Similarly, for species of conservation concern, richness was enhanced by increased landscape-level woodland cover at the 750m scale. Such assemblage-level associations can mask the responses of individual species. For example, some upland specialists, such as the red grouse and golden plover, were negatively associated with intensive grassland in the landscape, while other species of conservation concern, notably curlew, lapwing and snipe all showed positive relationships. These results indicate that upland agriculture at the landscape-scale is integral to maintaining the richness and composition of UK moorland birds and hence land management actions for moorland should not be limited to that habitat alone.

Disturbance, species loss and compensation: Wildfire and grazing effects on the avian community and its food supply in the Serengeti Ecosystem, Tanzania

AbstractAn important question in biodiversity studies is whether disturbances in ecosystems will cause a net loss of species or whether such losses can be compensated by replacement of other species. We use two natural disturbances, fire and grazing, to examine the response of bird and arthropod communities in grasslands of Serengeti, Tanzania. Both burning and grazing by migrant ungulates take place at the end of the rains in June–July. We documented the communities before disturbance, then 1, 4 and 20 weeks after disturbance on three replicate plots and compared them with three undisturbed plots. Birds were recorded by observation, arthropods from pitfall, tray trap and sweepnet samples. We expected that as the grass biomass was reduced by either disturbance, bird communities would change with concomitant change in arthropod food abundance. Alternatively, bird communities would change not with the absolute amount of food but with the greater accessibility of food as the grass structure changed from long to short grass. Results showed first that both bird species richness and abundance increased after both types of disturbance, but burnt sites showed a greater increase than that for grazed sites. Second, there was a change in bird species composition with disturbance. The functionally equivalent athi short‐toed lark (Calandrella athensis) was replaced by the red‐capped lark (Calandrella cinerea). Third, the abundance of most groups of arthropods was lower on disturbed sites than those on undisturbed sites, and the reduction of arthropod numbers was greatest on burnt sites. These results imply that bird abundance did not occur through an increase in arthropod abundance but rather through a change in the grass structure making food more accessible; and the higher predation could have caused the lower arthropod abundance. In addition, some bird species replaced others thus functionally compensating for their loss.

Conversational Noise Reduction as a Win-Win for Ecotourists and Rain Forest Birds in Peru

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