From 1983–2001, nest and chick losses in capercaillie and hazel grouse were studied in the mountains of Central Slovakia (Veľká Fatra Mts, Malá Fatra Mts, Kremnické vrchy Mts, Starohorské vrchy Mts, and Nízke Tatry Mts, 18°50’–19°10’E; 48°47’–49°19’N). Out of 75 capercaillie clutches 49 (65%) were destroyed. Out of 159 hazel grouse clutches 104 (65%) were destroyed. The main mammalian egg predators were stone marten (Martes foina), pine marten (Martes martes), mustelids (Mustela sp.), and red fox (Vulpes vulpes) (altogether 22%), wild boar (Sus scrofa) (9%), and brown bear (Ursus arctos) (3%). The predation pressure on capercaillie and hazel grouse nests decreased significantly during the incubation period (74% nest losses during the first half of May, 54% in the second half of May). Nest losses in both capercaillie and hazel grouse followed the fluctuation in small rodents, with lowest losses during peak year (57%) and highest losses during crash year (82%) and prepeak year (80%). Average number of capercaillie chicks accompanying a hen in June significantly decreased during the study period (5.0 in 1983, 2.6 in 2001). In contrast, in hazel grouse, no significant decrease in number of chicks per hen in June was recorded during the study period.
Parental care in which females attend their offspring is recorded in over 30 species of ground beetles. Despite this, there is no quantitative data on the fate of the offspring when the mother is experimentally removed. This paper investigates parental care in Pterostichus anthracinus (Coleoptera: Carabidae). The objectives of the study were to estimate: (1) egg survival when the female is removed; (2) the ability of females to defend their eggs from attack by predators; (3) the ability of females to repair a damaged nest in which egg attendance takes place. In the laboratory, the reproductive activity of P. anthracinus lasted four months (from May till August) and peaked in late June. Mean (± SE) number of eggs in each clutch was 25.25 ± 2.19. All of the egg clutches were guarded by a female. Female attendance had no effect on egg mortality due to microbial attack. The duration of embryonic development lasted on average 5.2–5.3 days, and did not differ between the groups with and without maternal care. In P. anthracinus maternal care is important in preventing egg mortality due to predators. In the laboratory the percentage mortality of eggs without maternal care due to predators was 100%. In the group in which females attended their eggs, percentage mortality of offspring due to predation was about 51%. Female ability to repair damaged nests is important in preventing dehydration and reducing predation pressure. This laboratory study provides the fi rst quantitative data on the importance of maternal care in ground beetles in determining the survival of their offspring.
The alternative prey hypothesis suggests that generalist predators switch from their primary prey to secondary when the former is scarce. We tested this hypothesis during a two-year study combining data on predation of ground dummy nests and the numbers of small mammal populations in a highly fragmented landscape in the Krušné hory Mts, the Czech Republic. A significant decrease of small mammal numbers between 2002 and 2003 was followed by a considerable increase of predation on artificial nests from 34% to 76%. Most of the nests (64.7% of the documented cases in 2002) were predated by medium-sized mammals such as marten and fox, common in our study area. Only 8.8% were predated by avian predators (corvids) occurring infrequently in our study area. The results support the alternative prey hypothesis and suggest that in the Krušné hory Mts the nesting success of ground nesting birds may vary strongly from year to year depending on the cycle phase of small mammals, the main prey of dominant predators.