Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 18

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
|
|
tom 49
|
nr 1
EN
Several studies have suggested dietary segregation between nestling and adult birds resulting from both dietary requirements of offspring and distance to the foraging sites. We examined the diet in terms of composition and dimension, as the weight, habitat and taxonomy of prey in nestling and adult male and female Bluethroats Luscinia svecica spp. cyanecula at a recently colonized area in a mosaic of wetland (with sewage water) and terrestrial habitats in south-west Poland. On the basis of faecal samples collected between 2009-2012 from several broods and 94 adults, we found that nestlings had significantly lower diet diversity, consisting of heavier prey items. Comparing the proportion of seven major food types (order of insects/invertebrate class) we showed that the diet composition of adult and nestling Bluethroats differed significantly. The diet of nestlings contained significantly more soft-bodied prey items, namely Diptera and Lepidopteran larvae, and significantly fewer Coleoptera and Hemiptera. Furthermore, since adult showed marked decrease (contrary to young Bluethroats) of diet diversity and number of prey in the progress of the breeding season, hence our entire findings can imply that nestlings are fed in a selective manner receiving more profitable (soft-bodied and terrestrial) prey, and adults adjust their diet consuming less profitable (more chitinized and smaller) prey. This ultimately suggests the partial dietary segregation between nestling and adult birds, both in the term of size (biomass) and composition of prey. The use of a broad spectrum of food items and various prey types, and particularly the low dependence of nestlings on aquatic insects, suggests that Bluethroats have very plastic dietary requirements, which is most likely a factor facilitating the recent population recovery and adaptation to ecotonal zones between moist/wetland and terrestrial habitats with abundant moist soil, in newly settled areas of Europe.
PL
W oparciu o analizę 161 odchodów (126 od dorosłych i 35 od młodych) zebranych w latach 2009-2012 porównano dietę i właściwości zdobyczy u dorosłych i młodych podróżniczków zasiedlających mozaikę biotopów wodnych i lądowych na polach irygacyjnych we Wrocławiu. Badania wykazały, że młode podróżniczki mają statystycznie istotnie niższą różnorodność diety (Fig. 1), jednak ich zdobycze były cięższe niż u ptaków dorosłych (Fig. 2 i 3). Porównanie składu diety (wyrażonej udziałami siedmiu głównych typów pokarmu) wykazało, że dieta młodych zawierała istotnie więcej „miękkich” zdobyczy: muchówek i gąsienic, a mniej chrząszczy i pluskwiaków (Tab. 1 i 2). Ponadto, w trakcie sezonu lęgowego dorosłe wykazały się znacznym spadkiem (w przeciwieństwie do młodych) różnorodności diety i liczby zdobyczy, stąd uzyskane wyniki mogą sugerować, że pisklęta karmione są w sposób selektywny, otrzymując lepsze (cięższe i bardziej miękkie) zdobycze, a dorosłe w tym czasie dostosowują swoją dietę zjadając mniejsze i bardziej schitynizowane zdobycze. To ostatecznie może wskazywać na częściową segregację diety pomiędzy pisklętami a dorosłymi podróżniczkami. Wykorzystywanie szerokiego spektrum taksonomicznego zdobyczy (Apendyks 1), a zwłaszcza niski udział bezkręgowców wodnych w diecie piskląt, sugeruje, że podróżniczki są generalistami pokarmowymi, co jest najprawdopodobniej czynnikiem ułatwiającym niedawną ekspansję terytorialną.
EN
Due to decrease in the area of extensively managed, semi-natural grasslands, that contribute to high biodiversity level preservation, the conversion of highly productive meadows to extensively managed, species-rich grasslands is now regarded as an important task for nature conservation. The aim of this long-term study was to assess the significance of restoration measures for diversity and trophic structure of above-ground insect community. That study challenges some weaknesses of previous studies as it was conducted with the use of suction trap enabling quantitative analyses of the changes in most insect taxa, and in a long time-span (1992–2005) in a set of permanent plots. The study area was located in a subalpine zone in Bavaria, near Laufen (Germany). The restoration process was initiated in 1996 by a cessation of fertilization and reduction of number of mowing to 1–2 per year. The changes in insect density and diversity (number of families) were monitored in ten restored and two reference plots with the aid of a suction trap. The changes in the insect community recorded during 14 years support findings from other studies that response of insect community to restoration process is usually slow on average. The short-term comparison in 2004–2005 between the restored and reference plots show that the first ones were characterized by more diverse (in term of family number) insect communities (as a whole as well as in guilds of predatory and parasitic species). From the other side, the long-term trend analysis shows that since 1998–2000 insect diversity and abundance was declining. Also trophic structure is fluctuating without clearly defined trend. These findings are in line with the results of the analyses of taxonomic composition similarity. They did not support the expectations neither that difference between initial and current taxonomical composition in a restored plot increases in time (mainly because of incoming new species), nor that spatial heterogeneity of insect assemblages should increase. However, spatio-temporal insect interactions between sample plots (located close to each other), linked to high movement ability of many insect taxa, could mask the changes in insect community caused by restoration.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.