ABSTRACT
The study aimed to determine the influence of grassland management on the potential food base of the red-backed shrike Lanius collurio and the condition of chicks in the population inhabiting semi-natural grasslands in the Narew floodplain. The grassland area was divided into three groups: extensively used meadows, intensively used meadows fertilised with mineral fertilisers, and intensively used meadows fertilised with liquid manure, and selected environmental factors that may influence food availability were determined. Using Barber traps, 1825 samples containing 53,739 arthropods were collected, and the diversity, abundance, and proportion of large arthropods in the samples were analysed depending on the grassland use type. In the bird population, the condition of the chicks was characterised by the BCI (Body Condition Index) and haematological parameters (glucose level, haemoglobin level, haematocrit, and H:L ratio). The diversity of arthropods was highest in extensively used meadows. Still, the mean abundance and proportion of arthropods over 1 cm in length differed significantly for Orthoptera, Hymenoptera, Arachne, and Carabidae between grassland use types, with the highest proportion of large arthropods and the highest abundance recorded in manure-fertilised meadows. The highest Body Condition Indexes and blood glucose levels of nestlings indicating good nestling nutrition were recorded in nests of birds associated with extensive land use. The H:L ratio as an indicator of the physiological condition of nestlings was high on manure-fertilised and extensively managed meadows, indicating stress factors associated with these environments. This suggests that consideration should be given to the effects of chemicals, such as pesticides or drug residues, that may come from slurry poured onto fields on the fitness of red-backed shrike chicks.
ABSTRACT
Agriculturally used meadows are habitats whose biodiversity depends on anthropogenic disturbances such as fertilization or mowing. Intensified agricultural practices (too frequent mowing, use of mineral fertilizers and insecticides) lead to declines in the abundance and species diversity of the biota inhabiting them. The intensification of agricultural production in north-eastern Poland relates primarily to the increase in cattle numbers and the intensification of grassland management, but many areas were included in Natura 2000 network. Our study was aimed at indicating the impact of diverse use of meadows on the species richness and diversity of invertebrates, amphibians, and birds in the grasslands of Narew river valley, Special Bird Protection Area, where the intensification of grassland use was noted in the last decades, and part of the meadows was included in the agri-environmental program. The agri-environmental program is a very good tool for the protection of grassland biotic diversity. The highest taxonomic richness and diversity of the studied animal groups were found in meadows included in these programs with extensive use, while the lowest was in the over- and intensively used meadows fertilized with mineral fertilizers and liquid manure. Only the meadows in the agri-environment program were inhabited by the fire-bellied toad and the tree frog - amphibians from Annex IV of the Habitats Directive. The number of breeding bird species globally threatened (IUCN Red List), listed in Annex I of the EU Birds Directive, and with negative population trend in Europe (SPEC1-3) was highest in meadows included in EU conservation programs. The main factors reducing biotic diversity in the grassland of flooded river valley were the high number of grassland mowing per season, intensive fertilization, especially with liquid manure, the great distance of meadows to the river, low soil humidity, and low share of shrubs and trees in the meadows border zone.
