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Different habitat use among three sympatric species of couas Coua cristata, C. coquereli and C. ruficeps in western Madagascar
Abstract
This study compares the habitat use by three species of couas, the Crested Coua Coua cristata, Coquerel's Coua C. coquereli and the Red-capped Coua C. rujiceps, in a dry forest at Ampijoroa, western Madagascar. The Crested Coua used higher layers (> 5 m) exclusively. Both Coquerel's and the Red-capped Coua stayed mainly on the ground, but the former used middle layers (1–5 m) for inactive behaviour (including resting, preening and basking) and whistling more frequently than did the Red-capped Coua. Both Coquerel's and the Red-capped Coua foraged almost exclusively on the ground but differed slightly in feeding technique. The Red-capped Coua took food on trails, relatively open areas in the forest, more frequently and more efficiently than Coquerel's Coua.
... Couas are a monophyletic group of endemic birds of Madagascar and belong to the Cuculidae (Langrand, 1990;Payne, 1997Payne, , 2005 There is no external morphological sexual dimorphism in these species. Previous works were conducted on some aspects of the ecology of Coquerel's Coua and Red-capped Coua (Appert, 1966(Appert, , 1970(Appert, , 1980Hawkins, 1994;Urano et al., 1994;Masuda & Ramanampamonjy, 1996). They are typically large insectivorous birds, and as such, are likely to be among the most sensitive bird species to deforestation (Thiollay, 1992). ...
... Season has to be considered an important factor for food availability in the foraging studies, and it is necessary not to pool all observations, if the aim of the study is to analyse the foraging behaviour. In this way, we considered Urano et al.'s (1994), obtained in the same station, as biased, because these authors did not take into consideration the effects of the seasonal variations. ...
... These differences can have an evolutionary significance, because Red-capped Coua would be more adapted to open environments, and Coquerel's Coua to a forested environment, as already suggested by Urano et al. (1994). Our own results suggest that the Red-Capped Coua is encountered in open habitats, which in Ampijoroa are also their most usual habitats (Chouteau, Fenosoa & Rakotoarimanana, 2004). ...
Coquerel's Coua (Coua coquereli) and Red-capped Coua (Coua ruficeps) occur in the western dry forest of Ankarafantsika in northwest Madagascar. This kind of forest is characterized by an alternating of a dry and a rainy season. Although they belong to the same genus, the two species differ in appearance, with Red-capped Coua being slender than Coquerel's Coua. We analyse their respective foraging strategies, according to the seasonal variation. The foraging behaviour of both species was different and was also influenced by the seasonal variations. They tended to use the same main substrates but differed in the proportion of foraging techniques according to the season. Seasonal variations probably have an important effect on the prey availability (estimated by the rate of prey capture), the nature of prey and also alternative foraging substrates used, forcing the two species to use different techniques and probably to capture different prey. These different foraging strategies could maintain the coexistence between these two species.
... To this end, the environmental factors (land cover, topography and climate) that drive Coua distribution in Madagascar were investigated using SDM, as well as the degree of habitat overlap between them. The relevance of this research lies in the fact that ecological studies about Couas are uncommon and the few that do exist focus mainly on microhabitat selection, foraging and breeding behaviour of only a few species (Chouteau, 2004(Chouteau, , 2007Chouteau & Fenosoa, 2008;Chouteau & Pedrono, 2009;Urano et al., 1993). To my knowledge, this is the first attempt to assess the spatial distribution of all Coua species by using macroscale environmental predictors. ...
... Even though no general pattern emerged from TA B L E 3 Hurlbert's index of niche overlaps among Couas that have at least 10% of their distributions overlapping. In bold the pairs with the strongest overlap, and in italics the pairs without niche overlap Coquerel's Coua appears to be linked to habitats with tall trees and large numbers of lianas and stems , whereas the Red-capped Coua is absent from habitats with large trees and forages more often where understorey vegetation is not well developed (such as burned areas or logged forests) (Chouteau, 2007;Chouteau & Fenosoa, 2008;Chouteau et al., 2004;Urano et al., 1993). Therefore, as expected, the different foraging strategies of ecologically similar species ensure they can coexist. ...
en Knowledge of the distribution and of the realised niche of a species is essential for an understanding of its ecology, especially in the case of poorly known species. To reach this goal, species distribution models (SDMs) can be developed to explain how environmental variables shape the distribution of species. The main aim of this research is to provide new insights concerning the nine species of Coua, endemic birds of Madagascar. This study is relevant because ecological studies on Couas are uncommon, and although these species are listed as Least Concern by IUCN, some of them are declining. The relationships between each species and the environment, particularly land cover, topography and climate, were investigated through MaxEnt. Next, the amount of niche overlap among species was calculated to investigate whether there is any spatial niche segregation. The results showed that the nine species of Coua select many habitat types, especially broadleaved forests, although some species also used mosaics of forests and croplands. Despite the lack of evidence of a larger spatial overlap between different Coua species with different habits than between species with similar habits, for many of them, there is overlap, which can mainly be explained by ecological and behavioural differences.
Résumé
fr La connaissance de la répartition et de la niche réalisée d’une espèce est essentielle pour permettre une bonne compréhension de son écologie, notamment dans les cas où cette même espèce est mal connue. Pour atteindre cet objectif, des modèles de distribution des espèces (SDM) peuvent être développés afin d’expliquer la façon dont les variables environnementales façonnent la répartition des espèces. L’objectif principal de cette recherche est d’apporter de nouvelles connaissances concernant les neuf espèces de Coua, oiseaux endémiques de Madagascar. Cette étude est pertinente, car les études écologiques sur les Couas sont rares et, bien que ces espèces soient classées dans la catégorie Préoccupation mineure sur la liste rouge de l’UICN, certaines d’entre elles sont en déclin. Les relations entre chaque espèce et l’environnement, en particulier l’occupation des sols, la topographie et le climat, ont été étudiées à l’aide de MaxEnt. Le degré de chevauchement des niches entre les espèces a ensuite été calculé afin de déterminer s’il existe une ségrégation spatiale au sein de ces mêmes niches. Les résultats ont montré que les neuf espèces de Coua sélectionnaient de nombreux types d’habitats, en particulier les forêts de feuillus. Cependant, certaines espèces utilisaient également des mosaïques de forêts et de terres cultivées. Malgré l’absence de preuves d’un chevauchement spatial plus important entre les espèces de Coua ayant des habitudes différentes qu’entre des espèces ayant des habitudes similaires, le chevauchement s’explique principalement par des différences écologiques et comportementales dans la plupart des cas.
... Langrand 1990; Morris and Hawkins 1998;Raherilalao and Goodman 2011;Safford and Hawkins 2013), but precise details in a quantitative sense on the forest strata occupied or daily shifts are poorly documented. Some studies have reported on the vertical distribution of Malagasy birds (Yamagishi et al. 1992;Urano et al. 1994;Rajaonarivelo 2016), but most of this work has focused on a species, a genus, or a specific family, and few details are available at the community level. This current study has two goals: 1) to document the vertical stratification of the avian community occupying a dry deciduous forest in central western Madagascar and 2) to document daily shifts in the vertical strata used by birds related to vegetation structure and temperature. ...
... These values were grouped into four strata as defined by Walther (2002): (1) canopy or upper layer equivalent to the space from 8 to 20 m with discontinuous crown (including emergent), (2) mid-story or middle layer from 2 to 8 m, (3) understory or lower layer from the ground and 2 m, and (4) ground layer which included litter, dead wood, and fallen tree trunks. Activities of birds were grouped into five categories: feeding (foraging behavior and food consumption), singing (vocalizing which included contact and alarm calls), moving (short flight or hopping in vegetation or walking on vegetation or ground), roosting (perching on different forms of support, resting, and sun basking), and preening (Urano et al. 1994;Partasasmita et al. 2017). ...
Data on the vertical distribution and ecological requirements of forest birds in western Madagascar are poorly documented. Strata use of forest-dwelling birds associated with vegetation structure and daily temperature patterns was examined in the dry deciduous forest of Kirindy. Six line transects of 1000 m each were used to survey birds and linear sampling to quantify vegetation structure. Data loggers were employed to record differences in temperature across vertical forest strata. A total of 3468 observations of 37 bird species were recorded. In the early morning, birds called frequently and used the canopy, at mid-day, when temperature in the upper strata increased on average around 7ºC, they tended to descend along a vertical gradient to the denser vegetation of the understory, presumably to avoid heat stress. In the case of largerbodied canopy birds, they occupied the mid-story during the heat of the day. Regardless of the time of the day, the mid-story was widely used by forest birds for feeding, roosting, and preening. These results demonstrate the sensitivity and vertical movements of birds to varying environmental conditions and provide new information on the ecology of Malagasy dry forest-dwelling birds.
... The West Madagascan dry forest is one of the 218 Endemic Bird Areas (EBAs) in the world (Stattersfield et al., 1998) and one of the EBAs granted critical conservation priority, in urgent need of protected areas. Knowledge of the avian assemblages of this EBA has increased during the last decade (c.f. for example, Andrianarimisa, 1993; Urano et al., 1994; Yamagishi, Urano & Eguchi, 1995). However, studies into the impact on the bird community of deforestation in this area have never, to our knowledge, been published. ...
... The forest preference of endemic bird species in relation to fire coincides with their known habitat use. Thus, Coua ruficeps is the most terrestrial coua in Ankarafantsika (Urano et al., 1994) and occurred exclusively in unburned forest in which the ground is mostly uncovered. Vanga curvirostris, which mainly forages in tree leaves, twigs and branches – between 5 and 20 m – was also found only in unburned forests (Yamagishi & Eguchi, 1996). ...
We studied the influence of vegetation structure and tree phenology on bird communities along a gradient of tropical forest degradation in NW Madagascar. Birds were censused by point counts at Ankarafantsika, one of the largest remnants of the severely reduced dry deciduous forest. The original forest was dominated by foliage insectivores. A few years after wildfire, regrowth was dense, most forest bird species were still present and additional understorey species appeared. As a result, species richness and abundance per point count increased. In contrast, when forest was transformed into savanna, the avian assemblage became poor, dominated by granivores and aerial insectivores, with only seven species shared with the original forest. Foliage volume, grass volume and bare ground cover explained most of the bird community variation by means of canonical correspondence analysis. Birds tended to increase their habitat breadth along the forest–savanna gradient. An index of bird conservation value, including abundance, endemism and the threatened status of the species, was highest in burned forests (1.12), intermediate in unburned forests (1) and lowest in savanna (0.44). The results emphasise the urgent need to protect not only the undisturbed fragments, but also the burned dry forests, because of their high value for biodiversity.
... The systematic relationships among cuckoo lineages (subfamilies) is uncertain. We wanted to address several questions in particular: (1) is there evidence for monophyly of cuckoo subfamilies; (2) what are the relationships among the subfamilies; (3) does the enigmatic hoatzin fall within the cuckoos, as suggested by some studies (Sibley and Ahlquist, 1990;but see Avise et al., 1994);(4)is the genus Coua, a group that shows considerable ecological variation (Urano et al., 1994), monophyletic; and (5) what are the relationships within the genus Coua? In this study, we wanted to determine the utility of mitochondrial protein-coding gene sequences in reconstructing a phylogeny for cuckoo lineages. ...
... Only genera that overlap with the genera in our study are included. largely terrestrial (Urano et al., 1994;Langrand, 1995). Furthermore, virtually all of the extant nine Coua species have distinct habitat distributions, occurring in either the dry forests in the west or the humid forests in the east. ...
The avian family Cuculidae (cuckoos) is a diverse group of birds that vary considerably in behaviors of interest to behavioral ecologists, e.g., obligate brood parasitism and cooperative breeding. The taxonomy of this group has historically been relatively stable but has not been extensively evaluated using molecular methods. The goal of this study was to evaluate phylogenetic relationships within the ecologically diverse genus Coua and the placement of Coua among major cuckoo lineages. We sequenced 429 bp of cytochrome b (cyt b) and 522 bp of ND2, both mitochondrial genes, for 26 species of cuckoos spanning 13 genera. We also included the enigmatic hoatzin (Opisthocomus hoazin) and used two Tauraco species as outgroups. ND2 exhibited higher rates of DNA sequence and amino acid substitution than cyt b; however, this did not greatly affect the overall levels of phylogenetic resolution and support provided by these two genes. Combined analyses produced two alternative phylogenies, depending on weighting scheme, both of which were fully resolved and were characterized by high bootstrap support. These phylogenies recovered monophyly for all of the traditional cuckoo subfamilies and indicated, with strong support, that the hoatzin is outside of Cuculidae. Within Coua, an arboreal and a terrestrial clade were identified. In contrast, habitat choice of Coua species did not greatly reflect the phylogeny.
... The present study was carried out during the early parts of their breeding season (from September 1997to January 1998and from September 1998to November 1998, when the lizards The study area (16.6ha) was a quadrat plot of a dry deciduous forest located at the Jardin Botanique A of Ampijoroa, Madagascar proximately 200m a. s. l. The vegetation was dominated by three species of Strichnos generally 9-12m in height (Razafy, 1987;Urano et al., 1994), and scattered shrubs and open areas with abundant leaf litter were present. The quadrat trails. ...
The spatial distribution pattern and associated social interactions of Oplurus cuvieri cuvieri were studied in a deciduous dry forest of Ampijoroa, Madagascar. Home range sizes were significantly larger in males than in females. In both sexes, snout-vent length was not correlated with home range sizes. Home range of males overlapped both inter- and intrasexually. Female home ranges rarely overlapped intrasexually. Consexual aggressive interactions indicated the presence of territoriality. Distribution pattern and observed intersexual interactions suggested a polygynous mating system. Site fidelity was observed for both home range and shelter tree levels. Tail breakage was moderately frequent, implying high predation pressure and the importance of safety refuge. No sexual differences were observed in thermal environment, perch height, or perch diameter, whereas sexual dimorphism in body size and dorsal color pattern was found. More than 80% of the lizards of both sexes performed “resting”.
... D'autre paramètre tel que la compétition peut aussi pousser l'animal à réguler son comportement afin de minimiser les impacts de ce paramètre. Chez les espèces d'oiseau du genre Coua (Cuculidae) de l'ouest de Madagascar par exemple, elles sont toutes insectivores et partagent le même habitat ; mais exploitent des strates arbustives différentes pour éviter une compétition interspécifique (Urano et al., 1994 ;Chouteau, 2003). Aussi, la prédation peut constituer un paramètre déterminant du comportement actuel des vertébrés, c'est entre autres le cas de la vie en groupe dans le but de se protéger des prédateurs (Altringham, 1996). ...
L’écologie comportementale de Rousettus madagascariensis (Pteropodidae),
une chauve-souris frugivore endémique de Madagascar qui forme une colonie dans une
grotte au sein la Réserve Spéciale d’Ankarana (extrême nord de Madagascar), est
rapportée dans ce travail Les activités diurnes de cette espèce ont été filmées dans la
grotte à l’aide d’un caméscope à lumière infrarouge en saisons sèche et humide, de
2017 à 2018. Différentes sessions de captures ont été effectuées dans la même grotte
entre 2014 et 2018. Les résultats ont indiqué une variation saisonnière significative de
tous les comportements filmés sous l’influence de la température régionale moyenne,
de la température et de l’humidité relative (rapport entre la pression partielle de la
vapeur d’eau dans l’air et la pression de vapeur saturée à la même température) à
l’intérieur de la grotte. La saison sèche était caractérisée par une faible valeur de
l’indice d’état corporel ou BCI (rapport entre le poids de l’animal et la longueur de
l’avant-bras), la fréquence élevée des comportements de repos, la consommation de
mouches ectoparasites hématophages, l’accouplement et la configuration en groupe
serrés des individus. Durant cette saison, il a été estimé 37 mouches ectoparasites
consommées par jour par un individu adulte de Rousettus, menant à une moyenne de
57 905 ectoparasites ingérés par jour par la colonie. Il n’y avait pas de différence
statistiquement significative entre le taux ingéré par les adultes mâles et femelles.
Pendant la saison humide, la fréquence des comportements de toilettage et de
déplacement (vol et rampement) était plus élevée ; les individus se regroupent d’une
manière desserrée avec une fréquence élevée des individus solitaires et les valeurs de
BCI étaient plus élevées. L'accouplement était principalement observé, par ordre
d’importance, au mois de septembre et juillet (saison sèche) ainsi qu’en janvier (saison
humide). Ce comportement était en correlation négative avec la précipitation. Les
accouplements entre le mois de juillet et septembre sont associés à des naissances,
juste avant ou pendant la saison des pluies, une période où les fruits sont les plus
abondants à Ankarana. Les accouplements du mois de janvier sont associés à des
parturitions en mi-avril ou vers le mois de juillet en cas de retardement de l’implantation
de l’oeuf, quand les fruits sont moins abondants. Les périodes de naissance
présentaient une synchronie inter-annuelle et semblaient principalement être régulées
par la précipitation et la température régionale.
... Our main research area consisted of JBA, the forest station of Ampijoroa (ca. 3 ha), trails between them (ca. 1 km), and the areas immediately surrounding them. The vegetation was dominated by three species of Strichnos trees (mostly 9-12 m in height: Razafy, 1987;Urano et al., 1994), and scattered shrubs and open areas with abundant leaf litter were present. The climate is mainly dominated by a rainy season from November to March alternating with a dry season from April to October. ...
Animal color patterns often have functions in thermoregulation, predation avoidance, and intraspecific communication. Examining intraspecific variation of color patterns is an effective approach to clarify their functions in a specific animal. We investigated the variation of dorsal color pattern within a dry forest population of the Madagascan iguanian lizard, Oplurus cuvieri cuvieri. Mark-and-recapture study showed that the number of dorsal black bands (DBBs) varies from one to seven, and often increases and decreases ontogenetically. Among four factors (snout-vent length, sex, age, and habitat) and three interactions between them, only sex and habitat had significant effects on the number of DBBs. Female lizards and lizards inhabiting a forested area tended to have more DBBs than males and those in an open habitat, respectively. All captive born hatchlings had seven DBBs, and juveniles reared under a 40W lamp retained more DBBs than those reared under a 60W lamp. This suggests that the number of DBBs of O. c. cuvieri is affected by thermal conditions, implying a thermoregulatory function of this color pattern. © 2005, The Herpetological Society of Japan. All rights reserved.
Couas (Coua, Cuculidae) are birds endemic to Madagascar. The breeding biology of three terrestrial species (Red-capped C. ruficrista, Cocquerel's C. coquereli and Giant Coua C. gigas) was studied in two sites (Ampijoroa and Kirindy) of the western dry forest. They are monogamous, faithful to the same partner from year to year and non parasite. Both members of the pair build the nest and raise the young. Because of an important nest predation rate (particularly in Coquerel's Coua which builds exposed nests), the young leave the nest early and flee on the ground, where their parents continue to feed them until they are able to fly. From then predation rate lowers. Low fecundity is probably counterbalanced by high adult longevity. Home range size was measured for each species, at different seasons and in habitats which differed in their degree of disturbance. Red-capped Coua and Giant Coua have larger home ranges than Coquerel's Coua. Detailed statistical analyses were possible only for Coquerel's Coua. In Kirindy, mean home range did not differ between logged and unlogged gallery forest, either for unpaired individuals (respectively 3.3 and 3.6 ha in each habitat) or pairs (2.4 ha in each habitat). On the other hand, mean home range was significantly larger in logged dry forest (5.3 ha for individuals and 8.2 ha for pairs) than in logged gallery forest. In Ampijoroa, individual home ranges were larger in unburned (3.6 ha) than in burned dry forest (2.8 ha) but there was no size difference in home range between unpaired individuals and pairs.
Food habit of the Malagasy spiny tailed iguana, Oplurus cuvieri, was investigated based on its fecal samples. This lizard belongs to the endemic Malagasy family Opluridae, for which natural diet had been poorly studied. We focused on the extent of ant-eating and herbivory because these traits are dietary characters often evolved in iguanian lizards. Among 65 fecal samples examined, 73.8% and 40.0% contained ants and plant matter, respectively. The plant matter included small twigs, leaves, flower buds, and fruit seeds. Ants tended to be found more frequently in the dry season than in the rainy season. There was a significant negative correlation between snout-vent length of the lizard and the proportion of ants in its feces. Our results, coupled with the previous direct observations on foraging behavior of the lizard, suggest that O. cuvieri is primarily a sit-and-wait predator largely depending on ants, but also occasionally exploits plant matter by active foraging.
On the basis of opportunistic observations, the preferred habitats of diurnal
raptors in the south-west of the Northern Territory are quantified in terms of
their vegetation structures and composition, and linked with foraging methods
and information on local diets. Broad interspecific differences in diel
activity patterns are also described. The evidence suggests that raptor
species in this part of arid Australia differ with respect to their foraging
times, habitats and methods, and that these differences relate to their
partitioning of food resources.
The ecomorphological adaptations and foraging heights in the endemic Velvet Asity (Philepitta castanea) were studied in Ranomafana rain forest, south-eastern Madagascar, from August to November in 1995 and 1996. The external morphology showed a short, slightly decurved, narrow bill, perching feet of moderate length, a short tail, and rounded wings. Data on aerodynamic aspects reveal a high wing loading and a small degree of slotting at the wing tip. Besides, quantitative data from the field indicate that: (1) the forest under-storey was frequently used for all behaviours (foraging, eliminative, and inactive behaviours), and (2) fruits were plucked more efficiently from perches than on the wing.
Animal color patterns often have functions in thermoregulation, predation avoidance, and intraspecific communication. Examining intraspecific variation of color patterns is an effective approach to clarify their functions in a specific animal. We investigated the variation of dorsal color pattern within a dry forest population of the Madagascan iguanian lizard, Oplurus cuvieri cuvieri. Mark-and-recapture study showed that the number of dorsal black bands (DBBs) varies from one to seven, and often increases and decreases ontogenetically. Among four factors (snout-vent length, sex, age, and habitat) and three interactions between them, only sex and habitat had significant effects on the number of DBBs. Female lizards and lizards inhabiting a forested area tended to have more DBBs than males and those in an open habitat, respectively. All captive born hatchlings had seven DBBs, and juveniles reared under a 40W lamp retained more DBBs than those reared under a 60W lamp. This suggests that the number of DBBs of O. c. cuvieri is affected by thermal conditions, implying a thermoregulatory function of this color pattern.
The forests in Madagascar are threatened by logging and burning. Because of their importance for biodiversity conservation, monitoring their animal populations is also important. We worked at two stations in the western dry forest where we studied three species of terrestrial couas in several forest plots, which differed in their degradation state. Some were burnt; others were logged. By measuring vegetation characteristics and bird densities, it was possible to indicate which characteristics were important for these birds and which conservation measures would be necessary to apply for this forest.
Brown and Striated Thornhills Acanthiza pusilla and A. lineata are abundant and widespread in forests of south-eastern Australia. The two species are similar in appearence and often occur together. However, the Striated Thornhill forages mainly in the subcanopy and canopy (> 75% of foraging observations) where it specialises in taking food from the foliage of eucalypts O 90% of observations). The Brown Thombill forages mainly in the shrub layer O 70% of observations) and takes prey from bark, debris and the leaves of a large variety of plants including eucalypts. Both thombills forage mainly by gleaning but the Striated Thombill commonly hang-gleans O 20% of observations), a behaviour rarely used by Brown Thombills (< 5% of observation). Because of their ecological differences, the two thombills respond differently to forest management. Striated Thombills are disadvantaged by logging, which reduces the amount of canopy and subcanopy vegetation, but Brown Thombills benefit from the increased amount of shrub and ground vegetation that results. Conversely, Brown Thombills are adversely affected by fires that reduce the amount of debris and low vegetation. In the absence of eucalypts, Striated Thombills are absent from pine (Pinus) plantations, but Brown Thombills may be abundant. The abundance of thombills, their wide distribution and different responses to forest management suggests that they could be useful in monitoring the health of forest ecosystems and for developing plans of management that take into account the differing requirements of forest wildlife.
To address whether foraging strategies affect habitat-use patterns of nonbreeding warblers, I quantified foraging behavior, bill dimensions, and diet (based on regurgitation samples) of Ovenbirds (Seiurus aurocapillus) and Swainson's Warblers (Limnothlypis swainsonii) wintering in three habitats in Jamaica. Ovenbirds primarily gleaned prey from the surface of the leaf litter (95% of foraging maneuvers), resulting in a diet comprised predominantly of ants (62% of all prey items), seeds (18%), and beetles (9%). Swainson's Warblers foraged by lifting leaves (80% of foraging maneuvers), resulting in a significantly different diet dominated by beetles (39%), spiders (22%), and ants (19%). More than 60% of the regurgitation samples from Swainson's Warblers contained orthopterans and/or gecko (Sphaerodactylus goniorhynchus) bones. Averaged across all habitat types, Ovenbirds consumed ants in direct proportion to their abundance based on visual counts of arthropods. Swainson's Warblers consumed beetles more than expected based on the abundance of beetles in visual counts and Berlese funnels. The use of a diversity of habitats by Ovenbirds may be related to their ability to feed opportunistically on ants, which are a widespread, abundant, and reliable resource. In contrast, based on their foraging behavior and diet, Swainson's Warblers may be restricted to habitats with a well-developed canopy and an abundant subsurface leaf-litter fauna.
Analysis of habitat use based on radio-tagged animals presents difficulties inadequately addressed by current methods. Areas of concern are sampling level, data pooling across individuals, non-independence of habitat proportions, differential habitat use by groups of animals, and arbitrary definition of habitat availability. We advocate proportional habitat use by individual animals as a basis for analysis. Hypothesis testing of such nonstandard multivariate data is done by compositional analysis, which encompasses all MANOVA/MANCOVA-type linear models. The applications to habitat use range from testing for age class, effects or seasonal differences, to examining relationships with food abundance or home range size. We take as an example the comparison of habitat use and availability. The concepts are explained and demonstrated on two data sets, illustrating different methods of treating missing values. We compare utilized with available habitats in two stages, examining home range selection within the overall study area first, then habitat use within the home range. At each stage, assuming that use differs from random, habitats can be ranked according to relative use, and significant between-rank differences located. Compositional analysis is also suited to the analysis of time budgets or diets.
Prolonged seasonal drought affects most of the tropics, including vast areas presently or recently dominated by 'dry forests'. These forests have received scant attention, despite the fact that humans have used and changed them more than rain forests. This volume reviews the available information, often making contrasts with wetter forests. The world's dry forest heterogeneity of structure and function is shown regionally. In the neotropics, biogeographic patterns differ from those of wet forests, as does the spectrum of plant life-forms in terms of structure, physiology, phenology and reproduction. Biomass distribution, nutrient cycling, below-ground dynamics and nitrogen gas emission are also reviewed. Exploitation schemes are surveyed, and examples are given of non-timber product economies. It is hoped that this review will stimulate research leading to more conservative and productive management of dry forests.
We quantified the behavior of four species of passerine birds foraging for arthropods among the foliage of different plant species and vertical strata of a northern hardwoods forest in New Hampshire (USA). Two species (Vireo olivaceus and Setophaga ruticilla) often changed their foraging patterns among strata but not among tree species, except in white ash. In the latter, both species flew more frequently between perches while searching for prey, which reflects the more open canopy and sparser distribution of ash foliage. A third species (Vireo philadelphicus) was stereotyped in its search and attack methods but had variable attack rates, indicating greater foraging success in some microhabitats than in others. The fourth species (Dendroica caerulescens), which inhabits the forest understory, showed few significant differences in its search or attack behavior, despite considerable variety in the sizes, shapes, and arrangements of leaves among available plant species. The foraging patterns of S. ruticilla were further influenced by differences among tree species in the abundance of a major prey type (leafhoppers, Cicadellidae: Homoptera) and by the active escape behavior of those prey.
We conclude that these four bird species, all of which search leaves at a distance and fly up to hover or snatch arthropod prey from leaf surfaces, are relatively unaffected by details of foliage structure such as leaf size, shape, petiole length, and arrangement on twigs. The distribution of foliage within a plant, however, and, in some cases, the abundance of certain food resources do differentially influence the foraging tactics and capture success of these species. Because foliage distribution and arthropod availability both vary with plant species, the floristics of a site will strongly influence the "foraging opportunities" available to birds and therefore their success in exploiting particular habitats.
The different searching tactics of passerine birds foraging for arthropods among the foliage of a northern hardwoods forest result in the capture of different kinds of prey. Five major searching modes are employed by the 11 foliage-foraging bird species in the Hubbard Brook Experimental Forest, New Hampshire. These are distinguished primarily by the rates and distances moved by the searching birds and by the types and forms of their prey-attacking maneuvers. These in turn reflect how large an area is scanned, how thoroughly it is searched, and how the bird moves from perch to perch in its search for prey. Mean searching and prey-attacking flight distances are positively correlated, indicating that birds move just far enough on average to take them into areas they have not previously searched visually. Likewise, birds that move rapidly while searching make significantly more prey attacks per unit time and hence encounter prey more often. Slow searchers scrutinize substrates more thoroughly and seem to take more cryptic and often larger prey. The results suggest that there are limitations on the ways that birds can search for and capture arthropod prey among foliage. We hypothesize that constraints imposed by the structure of the vegetation and by the types and abundances of prey determine the available foraging opportunities. Such habitat parameters may affect, in ecological or evolutionary time, the foraging traits of birds that can successfully exploit a particular habitat, and hence influence the patterns of bird habitat selection and community structure.
I studied intraspecific variation in foraging behavior of an endemic, insectiv- orous bird, the Elepaio (Chasiempis sandwichensis), in two Hawaiian forests that differed in degree of human modification. The undisturbed forest had a closed canopy, a dense under- story, and a groundcover of native plants. The disturbed forest had much lower tree and shrub densities, and a ground cover of alien grasses. Search-and-attack rates, proportions of attack maneuvers, and proportional substrate use differed between habitats. Birds in disturbed habitat attacked prey two-thirds as often as birds in undisturbed habitat, hopped less fre- quently, and flew farther and more often. They also did less perch-gleaning and chasing, did more flight-gleaning and hawking, used small branches and the ground less often, and used leaves and the air more often than birds in undisturbed habitat. Disturbed areas may be lower-quality foraging habitat because they require more difficult foraging methods. Age was associated with variation in search-and-attack rates and proportions of attack maneuvers, but sex was not. Subadult Elepaio attacked prey less often than adults, searched more slowly, and used simpler maneuvers more often, possibly to compensate for their lower proficiency. Log-linear analysis showed that attack maneuver was related to substrate and to tree species. Birds perch-gleaned more often on twigs and in ohia (Metrosideros polymorpha), hung more often on bark and in koa (Acacia koa), and flight-gleaned more often on leaves. Elepaio showed much flexibility in foraging behavior and used more-diverse attack maneuvers and substrates than related continental species, which may allow Elepaio to exploit disturbed habitats suc-
Measured abundance and distribution of Lepidoptera larvae, a major food type, on the foliage of the dominant tree species and the foraging behaviour used by birds to capture prey from foliage substrates. Larval abundances averaged 2.1 per 400-leaf sample, and differed significantly among tree species and strata and within and between years. Most larvae (78-91%) were found on leaf blades, with 62-75% on leaf undersurfaces. Bird species differed significantly in the frequencies at which they attacked prey on different foliage substrates and tree species. Several changed their foraging patterns from one tree species to another. Six of the 10 bird species directed attacks to substrates in proportion to the abundance of larvae there; the other 4 deviated from this pattern because of preferences for other kinds of prey or because of different abilities to perceive and capture prey from trees with differing foliage structures. Availability of food for forest birds is a function of 1) types and abundances of prey present, which vary among tree species; 2) foliage structure and characteristics of the trees, which influence prey detectability and accessibility; and 3) morphological and behavioural abilities of each bird species to perceive and capture those prey. Food availability therfore must essentially be determined separately for each bird species. -from Authors
The composition and structure of the bird community were investigated in French Guiana (northeastern Amazonia) 1 year and 10 years after selective logging and compared with bird community composition and structure in undisturbed primary forest. A point-count method was used in which 937 0.25-ha sample quadrats were censused for 20 minutes each. Whereas logging removed little more than 3 trees/ha, 38% of the forest undergrowth was destroyed and a proportion of the canopy was opened or damaged. An overall 27–33% decrease of species richness, frequency, and abundance occurred after logging, with a less marked decline of diversity and evenness indices, a substantial increase in the proportion of dominant species, and a 45% difference in species composition, weighed by frequency, between logged and undisturbed forest communities. Forty-two percent of the species from the primary forest decreased sharply or disappeared after logging and only 34% increased or remained unchanged. Microhabitat selection was the main correlate of sensitivity to disturbance. Most affected by logging were species associated with the understory of tall mature stands especially terrestrial species, members of mixed flocks, and solitary sallying insectivores, all of which decreased by 70% to over 90%. Most birds associated with canopy, small gaps, and vine tangles declined by only 10–30%. Small frugivores and species associated with clearings or edges increased. Among other factors, physiological intolerance of understory species to open forest microclimatic conditions (light, heat, or water stress) might influence their avoidance of logged areas. Timber harvesting generated a high level of disturbance, which depressed the bird diversity. After over 10 years of regeneration, the dense regrowth produced a uniform habitat type that still had not recovered the high species richness exhibited by the primary forest under an intermediate level of disturbance.
During the dry season in Costa Rica, sweep samples were taken of forest understory insects in three adjacent habitats of increasing moistness (Guanacaste Province: Areas I through III) and in another habitat under a much wetter precipitation regime (Limon Province; Area IV). These samples were then compared with respect to numbers of individuals, numbers of species, size frequencies, weight, developmental stages, species diversity, trophic levels, taxonomic composition and species exclusiveness. The absolute numbers of species increased from Areas I through IV; the numbers of individuals, frequency of small insects, dry weight, individuals per species and percent parasitic species increased from Areas I through III. The several indices of species diversity calculated for the samples only show partial agreement in relative values and trends. The data clearly demonstrate that adjacent tropical communities can have greatly different insect components. The possible effects of the differences between the insect communities of Areas I to III on vertebrate predators and plants are discussed. When compared with temperate data on insect communities there are indications that the four tropical communities examined have a much greater number of species and possibly a greater internal uniqueness than similar temperature communities.
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