Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 389

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 20 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  ptaki legowe
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 20 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The authors underline the importance of small, apparently unattractive habitat enclaves. They believe that a complete inventory of all such habitats in Poland should be done in the near future, and at least some of them should be placed under protection. The law on nature conservation provides for protection of such enclaves in the form of so-called ecological grounds. The example of small, 52-hectare Bugaj water reservoir, located in the Piotrków Trybunalski area, is given as an example which supports such a standpoint.
Inter-analyst variation was studied using the results of 15 mapping visits conducted by the author in 1992 in a 30-ha study plot in the oak forest in Moscow, Russia. During field work, special attention was paid to obtaining simultaneous records of singing birds. The average speed of the survey was 2.0-3.8 hours/10 ha. Identical sets of maps concerning 14 passerine species have been interpreted by five highly experienced European analysts and six Russian ornithologists with no previous experience of themapping method. Additionally, several ornithologists having previous experience in studying territorial behaviour of the Chaffinch Fringilla coelebs or Great Parus major and Blue P. caeruleus Tits evaluated maps of respective species. Within each of the four groups, the analysts showed a very high degree of mutual discrepancy. The coefficient of variation of estimates for 14 species varied from 21% to 87% among experienced analysts and from 45% to 90% among inexperienced ones. For each of 14 species, variation tended to be higher in the latter group. However, variances of estimates of experienced and inexperienced analysts differed significantly only for one of 14 species. Proportions between species were similarly reflected by different persons. The effect of "geographical" experience on the interpretation of results was not obvious.
The relationships between selected parameters of breeding bird communities and forest size were studied on the basis of the results of censuses done in 50 small forests (0.04-15.44 ha) situated in agricultural landscape of Eastern Poland. Even over this small range of forest size, the relations of different community parameters versus the logarithm of forest area exibited variability. The only straight-line relationship was between the species diversity and the forest area. Analysis of the relationships between the number of species, the proportion of non-breeding species, community evenness and density, has revealed tire existence of forest threshold sizes, separating different intervals of relations. This enabled a sequence of forest threshold sizes tobe worked out, relating the formation of bird communities with increasing forest size. Data drawn from the literature shown that, though differing in magnitude, the respective threshold sizes occur in similar sequence in other landscapes. This suggests the existence of a general schedule of breeding bird communities formation as forests increase in size.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 20 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.