Brigitte Poulin

Diets of land birds from northeastern Venezuela

We estimate diets of 68 bird species inhabiting dry seasonal habitats and mangroves of northeastern Venezuela, based on 3,419 birds forced to regurgitate using tartar emetic. Most birds were generalist feeders, including a wide variety of both invertebrate and plant taxa in their diet. Coleopterans, ants, and insect larvae were the most frequent invertebrate preys. Hummingbirds had low nectar intakes and differed from other species by feeding extensively on small soft-bodied arthropods. Most species fed on fruits to a variable extent. Actually, several species tended to be more frugivorous at our study sites than in previous reports.

Effect and Efficiency of Tartar Emetic in Determining the Diet of Tropical Land Birds

The effect and effectiveness of tartar emetic was tested on 82 bird species from 25 families and subfamilies inhabiting seasonal habitats of northeastern Venezuela. Of the 3,419 birds forced to regurgitate, 3,033 diet samples were obtained and 2,712 of them had recognizable food. Seventy birds (2%) died after administration of the chemical, but a smaller dosage or concentration reduced mortality in species more sensitive to the emetic. Overall, 24 invertebrate taxa and 59 fruit species were identified, with an average of 6 items per sample. Pollen grains were observed in 55% of the samples from nectarivorous species. Considering the low mortality, as well as the diversity of prey types and sizes found in samples, regurgitation using tartar emetic is probably the best method for determining the diet of land birds from various feeding habits.

Effect of winter cutting on the passerine breeding assemblage in French Mediterranean reedbeds

Common reed is increasingly harvested from the Mediterranean region toprovide thatching material to north European countries. The impact of thesemanagement practices on the fauna is poorly known. The aim of this study was toquantify the effect of reed cutting in the Mediterranean region through acomparative analysis of water regime, vegetation structure, arthropoddistribution and passerine assemblage at cut and uncut reedbeds in southernFrance. Cut reedbeds were characterised by a lower salinity, higher water levelin spring, and higher reed biomass than uncut reedbeds. Arthropod distributiondiffered consistently between cut and uncut sites, leading to a higher index offood available to passerines in cut reedbeds. Cut reedbeds had a similar birdspecies richness but a lower bird abundance, due to the significant decrease inMoustached Warblers and Bearded Tits at cut sites. The mild Mediterranean winterfavoured early growth of reed in spring, making harvested reedbeds suitable forbreeding of long-distance migrants such as the Great Reed Warbler and ReedWarbler. However, for the resident species that breed earlier in the season, cutreedbeds presumably lack sufficient vegetation cover to provide adequate nestingand feeding sites. Although biennial cutting (double wale) is considered as agood compromise between conservation and commercial interests in the UK, thejuxtaposition of annually cut and never cut reed patches appears as the onlysustainable alternative for the Mediterranean region. We further hypothesisethat an optimal mosaic design of cut/uncut reed patches could provide as high aconservation value as unmanaged reedbeds.

Characteristics of feeding guilds and variation in diets of bird species of three adjacent tropical sites

We studied feeding guild characteristics of birds in northeastern Venezuela in three adjacent tropical habitats: thorn scrub, thorn woodland, and deciduous forest. We mist-netted and marked birds twice monthly to obtain data on site tenacity. We determined diet by examining regurgitated food samples. Species were assigned to feeding guilds by a cluster analysis based on the proportion of the different food types found in their stomachs. Characteristics of each feeding guild from each habitat were submitted to a principal components analysis. Five parameters clearly distinguished feeding guilds: number of species, proportion of transient individuals, amount of seasonal variation in abundance, mean body mass, and estimated biomass. These parameters also appeared to be related to diet characteristics (food types taken, diet diversity) at the species level. Differences among habitats in food availability led to strong between-site differences in the diet of several species, and, accordingly, in their temporal and spatial patterns of abundance.

BUTORSTAR: a role-playing game for collective awareness of wise reedbed use

A role-playing game (RPG) supported by computer simulations, called BUTORSTAR, has been developed in the context of a LIFE-Nature European Programme (2001-2005) aiming to improve reedbed management for the conservation of a vulnerable heron, the Eurasian Bittern. The agent-based model simulates the impacts of reedbed management resulting from decisions made by farmers, reed harvesters, hunters, and naturalists. The model is based on an archetypal wetland made of a virtual landscape. Different water regimes are proposed, each one adapted to a particular wetland use. Land-use and water-management decisions are made by the players at both estate and management-unit levels. These decisions are entered into the model each year as the results of the negotiation process between the players. This RPG is designed to promote student awareness of (a) biological and hydrological interdependencies and their dynamics on different spatial and temporal scales, (b) the technical and socioeconomic factors involved in the different types of reedbed use, and (c) the usefulness of the negotiation process for establishing collective management rules. It is shown that BUTORSTAR creates a continuum of learning that crosses the traditional boundaries between disciplines and allows players to conduct multipurpose experiments that contribute to their comprehensive understanding of socioecosystems.

Settlement Period and Function of Long-Term Territory in Tropical Mangrove Passerines

We studied the territorial behavior of four insectivorous passerines residing in a tropical mangrove of northeastern Venezuela. Data were obtained through mist-netting and direct observation of color-banded individuals, regularly scheduled over two complete annual cycles. Seasonal variation in food resources (arthropods) and the birds’ diet also were evaluated. A chronological cluster analysis was used to determine the settlement periods of territories, the former being illustrated by the probabilistic Jennrich-Turner method. Three of the four species hold year-round territories. These long-term territories were settled only once a year, immediately after the breeding season when food was abundant. The territorial settlement was synchronous among all individuals ofa species, favoring strong modifications of the territorial mosaic. Considering the absence of territorial settlement prior to breeding and the high stability of territorial mosaics even during periods of low food abundance, territoriality during the non-breeding season primarily appears to ensure a breeding site for the next reproductive period. These results contrast with those from temperate regions where territoriality over the non-breeding season primarily enhances the survival of individuals during periods of food shortage.

QUANTIFYING THE BREEDING ASSEMBLAGE OF REEDBED PASSERINES WITH MIST-NET AND POINT-COUNT SURVEYS

Abstract Data collected in a 40-ha reedbed of southern France were used to compare the efficiency and limitation of mist-net and point-count techniques in estimating the composition and structure of a bird assemblage dominated by the Bearded Tit (Panurus biarmicus), the Moustached Warbler (Acrocephalus melanopogon), and the Reed Warbler (Acrocephalus scirpaceus). Null model analyses were used to determine the effect of spatial variability on estimates of species richness and relative abundance with the two sampling techniques. A 50-m net line operated during 5 h or two 50-m radius point counts of 10 min conducted 6 wk apart provided a similar estimation of species composition and relative abundance. While a sampling effort of 10 net lines or 13 point counts would permit the detection of a 25% difference in the relative abundance of most species (whether over time or among sites), the analyses on community structure suggest that 26 net lines or 13 point counts are necessary to sample adequately the structure of the bird assemblage (proportion of individuals from each species) in the 40-ha reedbed. This minimum sampling effort, however, is strongly influenced by the variance in number of individuals sampled, which differed among bird species. For instance, removal of highly mobile species such as the Bearded Tit, reduced by half the minimum sampling effort. To provide a reliable estimate of species richness and relative abundance, point counts must be based on both visual and auditory cues (30% of the birds sampled were silent), and be carried out at different periods to cover the early breeding season of any abundant species. While point counts are less demanding in the field, manipulation of netted birds permits the documentation of various aspects of their biology, which compensated for the increased time and effort needed.

Radiometric Normalization of SPOT-5 Scenes: 6S atmospheric Model versus Pseudo-invariant Features

We compared the efficiency and robustness of two radiometric correction techniques applied to six SPOT-5 scenes used for assessing environmental changes of Camargue wetlands: the 6S atmospheric model and 86 pseudo-invariant features (PIFs) found in deep water, pine trees, roofs and sand. The few PIFs were selected subjectively following the low number of potentially invariant sectors available on the scenes. Both approaches provided a similar radiometric variation (6S 4.3 percent; PIFs 4.0 percent). The latter increased from water to pine trees, to roofs and sand, with five reference points per feature being identified as cost effective. The withdrawing of variant features among the PIFs across dates or points caused a significant decrease in radiometric variation, especially with 6S (6S 2.8 percent, PIFs 3.4 percent). As many as 31 point per type of PIFs would be necessary to provide a radiometric variation that is not significantly different from that obtained with 6S, whereas nearly 300 and 4,000 points per feature would be required to provide similar or better results than the 6S code, respectively. Use of a few PIFs remains a valid approach, as long as the invariant sectors cover a wide range of brightness and are represented by objects of which the radiometric variation has preliminarily been tested.

Accuracy of bittern location by acoustic triangulation

Abstract Ecological studies and population surveys sometimes require information on the position of individuals. Because many birds are more audible than visible, we tested the potential of acoustic triangulation for locating Great Bitterns (Botaurus stellaris) within extensive reed marshes in the Camargue, France. During the breeding season, and predominantly at dawn, male bitterns produce a series of loud calls (booms). In the field, the direction of booming was estimated with a bearing compass by an observer walking along a linear path at the reedbed edge, taking enough measurements to cover a 90° wide angle between the first and last bearing. We used a probability model with an Andrews estimator to locate each bittern based on the intersection point of the bearings taken in the field. Bearing error was estimated by comparing these bearings with those derived from the real or estimated bird position. In a first experiment, we identified the factors influencing the variation in bearing error using six observers, 237 directional bearings, and 19 bitterns. In a second experiment, we quantified the bearing accuracy under optimal conditions based on three observers using 47 directional bearings to locate a bittern of known position. There was no observer effect, but wind speed above 10 km/h, occurrence of poor booms, and bittern distance under 200 m significantly increased bearing error. Bitterns calling normally under windless conditions could be located with a mean bearing accuracy of ±13.6°. Location accuracy depended primarily on the bird distance and number of bearing angles. We propose an optimal bearing effort to locate booming males in large reedbeds with an accuracy of a 40-m radius irrespective of the bittern distance. This protocol can be applied to other bird species once the bearing accuracy corresponding to their call and habitat has been estimated. Acoustic triangulation appears to be a useful, non-invasive, technique for locating bitterns and other bird species.

Contribution of rainfall vs. water management to Mediterranean wetland hydrology

Mediterranean wetlands are increasingly managed to maintain their functions and services following modification in water allocation, embankment and climate change, calling for proactive and adaptive water management. In a first step, we used long-term monitoring of water levels in 37 adjacent embanked marshes in the Camargue as a repeated non-controlled experiment to build a hydrological model. Without information on water input/output by marsh users, we could nevertheless estimate evapotranspiration under flooding and dry conditions, and soil water coefficient. The model provided a high predictive accuracy (adjusted R2?=?0.73-0.83) of monthly water levels when applied to an independent sample of 12 marshes. In a second step we developed an interactive decision-aid tool that allows users to visualize the impact of their management strategy (desired water level at a specific month) on subsequent water levels, and their consequence on different components of the ecosystem over a 10-yr period. Bimonthly monitoring of water levels (37 adjacent marshes, 10 yrs) used to develop a generic hydrological model for Mediterranean marshes fed by surface water.Model validation provided a high predictive accuracy for 12 tested independent marshes.A web interface developed to orient water management, allowing users to visualise impacts on the marsh flora and fauna.