scholarly journals Specialist predation covaries with colour polymorphism in tawny owls

2021 ◽  
Vol 75 (3) ◽  
Author(s):  
Patrik Karell ◽  
Kio Kohonen ◽  
Katja Koskenpato
Keyword(s):  
Small Mammals ◽  
Prey Availability ◽  
Food Resource ◽  
Food Resources ◽  
Colour Polymorphism ◽  
Generalist Predator ◽  
Colour Morph ◽  
Tawny Owl ◽  
Main Prey ◽  
Main Food

Abstract Understanding intraspecific phenotypic variation in prey specialisation can help to predict how long-term changes in prey availability affect the viability of these phenotypes and their persistence. Generalists are favoured when the main food resources are unpredictable compared to specialists, which track the availability of the main prey and are more vulnerable to changes in the main food resource. Intraspecific heritable melanin-based colour polymorphism is considered to reflect adaptations to different environments. We studied colour morph-specific diet specialisation in a generalist predator, tawny owl (Strix aluco), during offspring food provisioning in relation to mammal prey density. We hypothesised that the grey morph, with higher fitness than the brown in Northern boreal conditions, is more specialised in mammalian prey than the brown morph, which in turn has higher fitness than the grey in the temperate zone. We found a higher diversity of prey delivered to the nest by brown fathers compared to grey ones, which also depended on the overall mammalian prey availability. Brown fathers provided proportionally fewer mammalian prey than grey in poor, but not in favourable mammal prey years. Our results suggest that the brown morph is more generalistic and reacts more strongly to variations in food supply than the grey morph, which may be a beneficial strategy in an unpredictable environment caused by environmental degradation. Significance statement Diet choice of a species may vary depending on fluctuations in the abundance of their food resource, but also within a population, there can be adaptations to use different food resources. The tawny owl exhibits a grey and a reddish-brown colour morph and is considered a generalist predator eating both mammal and bird prey. We find that the diet of the reddish-brown morph is more diverse than that of the grey. When the tawny owls’ main prey, small mammals, are abundant both colour morphs prey on mammals, but in years with less small mammals, the reddish-brown morph is more prone of switching to small bird predation than the grey. The generalist strategy of the brown morph is likely to be more favourable than a stricter specialisation in small mammals of the grey under recently reoccurring irregularities in small mammal dynamics.

scholarly journals Aquatic insects as the main food resource of fish the community in a Neotropical reservoir

2009 ◽  
Vol 7 (4) ◽  
pp. 701-708 ◽  
Author(s):  
Ana Paula Vidotto-Magnoni ◽  
Edmir Daniel Carvalho
Keyword(s):  
Aquatic Insects ◽  
Food Resource ◽  
Gravimetric Method ◽  
Stomach Contents ◽  
Food Resources ◽  
Food Category ◽  
Main Food ◽  
Tietê River ◽  
Two Samples ◽  
Terrestrial Insects

We evaluated the feeding of fish species of the Nova Avanhandava Reservoir, low Tietê River, São Paulo State, Brazil. Fishes were collected in two stretches of the reservoir: Santa Bárbara (14 samples) and Bonito (two samples) between September 2002 and March 2004, using gill and seining nets. The results of stomach contents analysis were expressed with the frequency of occurrence and gravimetric method, combined in the Alimentary Index (AI). The 20 species studied consumed 52 food items, grouped in 10 food categories: aquatic insects, terrestrial insects, crustaceans, fish, macroinvertebrates, microcrustaceans, algae, vegetal matter, detritus/sediment and scales. The aquatic insects (mainly Chironomidae, Odonata and Ephemeroptera) were the most common food resources, consumed by 18 species. The diet composition of the community (species grouped) indicated that the dominant food category in the diet of fishes was aquatic insects (AI = 77.6%), followed by crustaceans (AI = 7.1%). Four trophic guilds were identified according a cluster analysis (Pearson distance): insectivorous (10 species), omnivorous (4 species), detritivorous (3 species) and piscivorous/carcinophagous (3 species). Despite the highest number of species, the insectivorous guild was responsible for more than 80% in captures in number and biomass (CPUEn and CPUEb). The low values of niche breadth presented by all species, along with the low values of diet overlap between species pairs indicate a high degree of food resources partitioning among species. The aquatic insects, despite being the main food resource of insectivorous fishes, also complemented the diet of other species, which demonstrate the importance of this food resource for the fish community, sustaining a high diversity, abundance and biomass of fishes.

Food resource partitioning between two sympatric temperate wrasses

2017 ◽  
Vol 68 (12) ◽  
pp. 2324 ◽  
Author(s):  
Mauro Sinopoli ◽  
Renato Chemello ◽  
Antonino Vaccaro ◽  
Marco Milazzo
Keyword(s):  
Resource Use ◽  
Prey Availability ◽  
Atlantic Coast ◽  
Food Resource ◽  
Stomach Contents ◽  
Food Resources ◽  
Sea Bottom ◽  
Over Dispersion ◽  
Labrid Species ◽  
Food Resource Partitioning

The present study analysed two sympatric wrasses, Thalassoma pavo and Coris julis, with similar sizes and morphologies, that are widespread in the reef habitats of the Mediterranean and the eastern Atlantic coast. Ocean warming has induced the northward movement of T. pavo, whereas C. julis has been moving to deeper habitats. In addition, under conditions of high slope of the sea bottom, T. pavo occupies shallow habitats and C. julis is in greater abundance in deeper habitats. By investigating stomach contents and prey availability in the benthos, we assessed whether the two wrasses exploit food resources by choosing different prey within the same habitat both under co-existence and segregation conditions. The results showed that T. pavo mainly feeds on gammarids and sipunculids, whereas C. julis mainly feeds on Alvania spp. and Paguroidea. The two wrasses also showed an intrinsic partitioning of food resources, independently of the condition of co-existence or segregation and benthic prey availability in the environment. The two wrasses fall in the ‘over dispersion of resource use’ model, in which species share numerous niche dimensions in a variable manner. Our findings may contribute to exclude a greater trophic competition between these labrid species in a projected warming scenario.

scholarly journals Age and sex differences in numerical responses, dietary shifts, and total responses of a generalist predator to population dynamics of main prey

Oecologia ◽  
2020 ◽  
Vol 192 (3) ◽  
pp. 699-711 ◽  
Author(s):  
Giulia Masoero ◽  
Toni Laaksonen ◽  
Chiara Morosinotto ◽  
Erkki Korpimäki
Keyword(s):  
Small Mammals ◽  
Prey Species ◽  
Generalist Predator ◽  
Predator Population ◽  
Alternative Prey ◽  
Sex Composition ◽  
Food Stores ◽  
Main Prey ◽  
Dietary Shifts ◽  
Age And Sex

AbstractFluctuations in the abundance of main prey species might shape animal communities, by inducing numerical responses and dietary shifts in predators. Whether numerical responses and dietary shifts differ among individuals of different age and sex has so far gained little attention. These differences could affect how much predators consume main and alternative prey, thus causing variation in predation pressure on main and alternative prey species. We studied the effect of fluctuating main prey abundance (voles) in autumn on the age and sex composition of a food-hoarding population of Eurasian pygmy owls Glaucidium passerinum (327 individuals), and on the species composition of their food stores in western Finland during 2003–2017 (629 food stores). Numbers of yearlings (< 1-year old) of both sexes and adult (+ 1-year old) females increased with increasing vole abundance. During low vole abundance, adult owls stored more small birds and less small mammals than yearlings. Females stored more small mammals than males and showed a tendency to store less birds. The amount of consumed birds (the most important alternative prey), and in particular of crested, willow, great, and blue tits, increased with low vole densities. Our results show that numerical, functional, and total responses of pygmy owls, and probably also other vertebrate predators, to the availability of the main prey in winter are shaped by the age and sex composition of the predator population, which both show large spatio-temporal variation in boreal forests.

scholarly journals Prey, management and landscape requirements of an endangered population of the Woodlark Lullula arborea in Southwest Germany

2021 ◽  
Author(s):  
Verena Rösch ◽  
Pascal Aloisio ◽  
Martin H. Entling
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Ground Cover ◽  
Main Food ◽  
Vegetation Height ◽  
Endangered Population ◽  
Rhine Valley ◽  
Territory Selection ◽  
Main Food Source ◽  
Upper Rhine

AbstractVineyards can be valuable habitats for biodiversity conservation. For example, in Rhineland-Palatinate (Germany) over a third of the state’s critically endangered Woodlark (Lullula arborea) population breeds in vineyards along the western margin of the Upper Rhine Valley. We here aim to elucidate how local ground cover management, food availability and the proximity to settlements affect territory selection by this bird species in the region. As climate, site conditions and management differ greatly from more continental or Mediterranean wine-growing areas, conditions for Woodlark conservation may differ as well.We compared 26 Woodlark territories in vineyards with 26 nearby reference areas from which Woodlarks were absent. We recorded vineyard ground cover in the inter-rows (% cover) as well as vegetation height and composition (forbs vs. grasses). Arthropods were sampled using pitfall traps, since they are the main food resource of Woodlarks during the breeding season. In addition, the distance to built-up areas was measured. The vegetation in Woodlark territories was shorter (mean 14.2 vs. 19.6 cm) and more dominated by forbs (39% vs. 27% cover) than in absence areas. The vegetation cover in the inter-rows had no effect on Woodlark territory presence or absence. Woodlarks also favoured areas with a higher abundance of arthropods (mean abundance 69.1 vs. 57.5) and a greater distance to built-up areas (mean distance 554 vs. 373 m). We conclude that to promote the Woodlark in wine-growing areas, short, forb-rich swards should be created, facilitating arthropod detectability. This is likely to require low levels of nitrogen fertilization since fertilizers favour tall-growing grasses that outcompete forbs. Pesticide applications should be kept at a minimum to enhance arthropods as the main food source for Woodlarks and their chicks. In addition, the expansion of settlements into breeding areas of Woodlarks should be avoided.

scholarly journals Diet seasonality and food overlap of the fish assemblage in a pantanal pond

2008 ◽  
Vol 6 (4) ◽  
pp. 567-576 ◽  
Author(s):  
Gisele Caroline Novakowski ◽  
Norma Segatti Hahn ◽  
Rosemara Fugi
Keyword(s):  
Fish Assemblage ◽  
Food Resource ◽  
Fish Fauna ◽  
Diet Breadth ◽  
Food Resources ◽  
Dry Season ◽  
Trophic Guilds ◽  
Trophic Specialization ◽  
Mato Grosso ◽  
Mean Values

We assessed the trophic structure of the fish fauna in Sinhá Mariana pond, Mato Grosso State, from March 2000 to February 2001. The aim was to determine the feeding patterns of the fish species during the rainy and dry seasons. The diets of 26 species (1,294 stomach contents) were determined by the volumetric method. Insects and fish were the most important food resources: insects were the dominant food of 23% and 27% of the species, respectively, in the rainy and dry season, and fish was the dominant item for 31% of the species in both seasons. Cluster analysis (Euclidean Distance) identified seven trophic guilds in the rainy season (detritivores, herbivores, insectivores, lepidophages, omnivores, piscivores and planktivores), and five trophic guilds in the dry season (detritivores, insectivores, lepidophages, omnivores and piscivores). The smallest mean values of diet breadth were observed for the specialist guilds (detritivores, lepidophages and piscivores), in both seasons. The widest means for diet breadth were observed for the omnivores, regardless of the season. In general, there was no seasonal variation in feeding overlap among the species studied. At the community level, diet overlap values between species were low (< 0.4) for 80% of the pairs in each season, suggesting wide partitioning of the food resource. The fish assemblage showed a tendency toward trophic specialization, regardless of the season, although several species changed their diets. We might consider two non-excludent hypothesis: that there is no pattern on the use of seasonal food resources and/or probably there are several patterns, because each one is based on characteristics of the studied site and the taxonomic composition of the resident species.

scholarly journals Gut content analysis of cattle egrets (Bubulcus ibis) in Asam Kumbang Crocodile Park, North Sumatra

2021 ◽  
Vol 912 (1) ◽  
pp. 012105
Author(s):  
E Jumilawaty ◽  
N Namira ◽  
A Anggelicha ◽  
A Hartanto
Keyword(s):  
Content Analysis ◽  
Prey Species ◽  
Prey Availability ◽  
Biological Control Agent ◽  
Food Resource ◽  
Control Agent ◽  
Gut Content Analysis ◽  
Gut Content ◽  
Dominant Group ◽  
Bubulcus Ibis

Abstract Cattle egret (Bubulcus ibis) is a widespread avian species inhabiting a variety of natural and artificial sites. Asam Kumbang Crocodile Park is one of establishments that occupied some portions of B. ibis habitat with no recent information on the food resource and prey availability for the viability of B. ibis. To this aim, we collected 10 random individuals of B. ibis to be sacrificed for gut content analysis of prey species. A total of 19 taxa was found as prey items in the gut of B. ibis with the dominant group from insects (Orthoptera, Scolopendromorpha). The diversity of prey species was categorized as moderate with intraspecific diet variation which formed four guilds that fed on specific taxa namely Group 1 (Haplotaxida, Lepidoptera, Anurans), Group 2 (Blattodea, Coleoptera, Araneae), Group 3 (Orthoptera, Scolopendromorpha); and Group 4 (Dermaptera, Squamata). Oxya chinensis and Oxya velox are important rice grasshopper pests that were also found in the gut of B. ibis reflecting their potential function as biological control agent.

scholarly journals Individual Variation in Predatory Behavior, Scavenging and Seasonal Prey Availability as Potential Drivers of Coexistence between Wolves and Bears

Diversity ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 356
Author(s):  
Andrés Ordiz ◽  
Cyril Milleret ◽  
Antonio Uzal ◽  
Barbara Zimmermann ◽  
Petter Wabakken ◽  
...  
Keyword(s):  
Prey Availability ◽  
Interspecific Interactions ◽  
Brown Bear ◽  
Predatory Behavior ◽  
Early Summer ◽  
Gray Wolf ◽  
Apex Predators ◽  
Main Prey ◽  
Large Carnivore ◽  
Age Class

Several large carnivore populations are recovering former ranges, and it is important to understand interspecific interactions between overlapping species. In Scandinavia, recent research has reported that brown bear presence influences gray wolf habitat selection and kill rates. Here, we characterized the temporal use of a common prey resource by sympatric wolves and bears and described individual and seasonal variation in their direct and/or indirect interactions. Most bear–wolf interactions were indirect, via bear scavenging of wolf kills. Bears used >50% of wolf kills, whereas we did not record any wolf visit at bear kills. Adult and subadult bears visited wolf kills, but female bears with cubs of the year, the most vulnerable age class to conspecifics and other predators, did not. Wolf and bear kill rates peaked in early summer, when both targeted neonate moose calves, which coincided with a reduction in bear scavenging rate. Some bears were highly predatory and some did not kill any calf. Individual and age-class variation (in bear predation and scavenging patterns) and seasonality (in bear scavenging patterns and main prey availability of both wolves and bears) could mediate coexistence of these apex predators. Similar processes likely occur in other ecosystems with varying carnivore assemblages.

scholarly journals Aggregations of Southern Caracaras (Caracara plancus) in soybean plantations in central Cerrado, Brazil

2019 ◽  
Vol 27 (1) ◽  
pp. 53-55 ◽  
Author(s):  
Dárius Pukenis Tubelis
Keyword(s):  
Small Mammals ◽  
Food Resources ◽  
Grain Production

AbstractThis study reports on large aggregations of Southern Caracaras (Caracara plancus) in soybean plantations in the surroundings of Parque Nacional das Emas, southwestern Brazil. Observations were done during harvesting activities in February 2009. Aggregations were found by driving a vehicle through roads that crossed or bordered soybean plantations located at less than 4 km from this park. For each aggregation detected, individuals found around harvesting machines were counted. The abundance of Southern Caracaras of each aggregation ranged between 76 and 104 individuals (n = 8). Despite the attraction of high numbers of caracaras to proximities of machines, most of them appear to do not obtain much food resources during harvesting of soybean fields. Caracaras were seen capturing small mammals, lizards, birds and large insects. This association between C. plancus and harvesting activities can be considered as opportunist behavior in response to rapid modification of grain-production landscapes in the Cerrado.

Freshwater Mussels as a Prehistoric Food Resource

1974 ◽  
Vol 39 (3) ◽  
pp. 421-434 ◽  
Author(s):  
Paul W. Parmalee ◽  
Walter E. Klippel
Keyword(s):  
Mississippi River ◽  
Freshwater Mussels ◽  
Food Resource ◽  
Food Resources ◽  
Archaeological Sites ◽  
Eastern North America ◽  
Subsistence Economies ◽  
Level Data ◽  
Food Potential ◽  
Prehistoric Subsistence

AbstractThe explication of prehistoric subsistence economies has been of increasing interest to archaeologists. This emphasis is reflected, in part, by the considerable attention afforded faunal analyses in the recent archaeological literature. However, little effort has been made toward developing methods that permit meaningful comparisons of food resources at the interspecies level. Data pertinent to the calculation of both quantitative and qualitative food potential of many of the vertebrate animals represented in archaeological contexts are extant. These data are lacking for freshwater mussels, frequently found in archaeological sites in eastern North America. Information relevant to determining the food energy provided by freshwater mussels common to much of the Mississippi River drainage is presented. Results are applicable to more credible interpretations of prehistoric subsistence as related to animal food resources.

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