Fragments of idle fields in urbanized zones may attract threatened bird species to nest, but, at the same time, may be favoured by generalist nest predators attracted by food resources abundant in urban areas. Only few studies have analysed effects of nest predation risk in suburban habitat fragments while considering the character of the surrounding landscape. We used artificial nests to examine possible effects of patch size and edge distance, extent of surrounding urbanization, habitat composition and heterogeneity on nest predation risk to ground-nesting birds in idle fields within suburban areas. Nest predation risk varied regardless of patch size. Edge effect appeared only combined with the proportion of particular habitat types in the surrounding landscape. Character of surrounding landscape was strongly influential. In particular, predation risk was positively correlated with proportions of unstable disturbed sites nearby but negatively
correlated with proportions of adjacent meadows and forests. From the standpoint of nature conservation and effective support to bird diversity in suburban areas, we highlight the importance of diverse nature-like stands such as meadows or forest fragments.
Birds protect their nests against predators in various ways. In addition to active defence, they can hide their nests or use the protection of other species breeding nearby that actively defend the nests. Studies evaluating these strategies simultaneously are rare, especially from areas unaltered by humans. Nest predation risks were studied in a wetland bird community at Lake Baikal, Russia. The community contained several species actively defending their nests, although most were “passive defenders”. Such tactics as active defence, concealed nesting, neighbourhood nesting and coloniality were tested for their effects on predation risk. The main predators
were birds, particularly carrion crows (Corvus corone). Analysis of 193 nests using multimodel inference based on Akaike’s information criterion
suggests the most successful tactic was active nest defence, although most birds applying this tactic build open (uncovered) nests. Passive defenders effectively reduced this risk by nest concealment and/or breeding near active defenders. Opposing patterns were found for active versus passive defenders near the most successful breeder but also a potential nest predator, the Mongolian gull (Larus mongolicus). Conservation implications emphasize support for large aggregations of active nest defenders, vegetation cover providing good nest shelter, and sufficient area of interior habitat reducing edge effects.
Predators use various tactics to find and depredate bird nests. This study examines a possible tactic of visually orientated predators termed “delayed nest-visit”. This consists in remembering the positions of incubating parents and subsequent easy depredation of eggs when the parents are away from their nests. Conditions for use of this tactic were experimentally simulated by installing artificial nests with quail eggs and plastic dummies of northern lapwings (Vanellus vanellus) at 11 actual breeding grounds with various
habitat conditions in southern and eastern Bohemia, Czech Republic. Habitat, presence of the dummy, and their interaction significantly affected nest survival. While 17.2 % of the nests baited with the dummy were depredated, this occurred in only 6.9 % of the nests without the dummy. This depredation rate was affected by the visibility of the dummies in particular habitats. The results suggest that predators may remember the nest position to delay their first visit to a previously located bird nest from a remote place and may use
this tactic to easily capture the clutches. The use of this tactic showed that at least some predator species are able to apply much more sophisticated approaches in search of birds’ nests than previously assumed.
We studied the possible role of clutch crypsis in antipredator behaviour in two related species of ground-nesting waders with camouflaged eggs, the northern lapwing (Vanellus vanellus) and the little ringed plover (Charadrius dubius). We examined whether this behaviour appears regularly in both species and tested the difference in the use of this trait between the two species. The results suggest that both charadriids rely on egg crypsis as a reasonable strategy toward avian nest predators. However, the larger and more conspicuous lapwings use it less frequently than plovers, probably because they rather rely on body size and aggressiveness combined with colonial breeding. Smaller and solitary little ringed plovers tended to hide the nest location more thoroughly than lapwings, probably due to their limited ability to defend the nest actively. Instead of aggressive attacks, they use alternative behavioural elements intended to deceive predators, namely incubation-feigning. Although egg crypsis is regularly used as a passive strategy for protecting nests against predators in both species, it seems to be unprofitable as an exclusive form of nest protection. The birds combine it with other behavioural elements, such as the above mentioned aggressiveness or incubation-feigning.
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.
Modern forestry may alter avian reproductive success indirectly through affecting predator-prey interactions. Here we evaluate the influence of road types on nest predation of ground-nesting birds in a highly fragmented forest area interspersed by a dense network of roads and forest paths, with one third of the area covered by a red-deer enclosure. Experimental nests (n = 276) resembling black grouse ( Tetrao tetrix) nests were proportionally installed along three types of roads discriminated by utility (road type, from frequently used to unused: tarred roads, gravel roads and forest paths) and inside/outside the red-deer enclosure. The nests were placed in couples, with one nest placed close to the road edge and the second placed inside the surrounding forest habitat to assess the “travel line” hypothesis. The “travel line” hypothesis was not supported because there was a similar predation rate among edge and interior nests. Even if predators can be discouraged along busy roads, type of road also did not affect nest predation. Nevertheless, nest predation inside the enclosure was significantly lower than in the surrounding, suggesting that frequent human disturbances in these habitats may have a repellent effect on predators of ground nests.
A three-year experimental study with artificial ground nests was carried out in a highly fragmented agricultural landscape in Southern Bohemia, Czech Republic, to examine whether population density or spatial distribution of active black-billed magpie (Pica pica) nests contributes to the pattern of predation on dummy nests. Out of the total of 335 dummy nests with a known fate, predators robbed 126 (37.6%). The population density of magpies did not affect nest predation significantly, while nests placed closer to active magpie nests were predated significantly more than distant nests in two out of the three years under study. Moreover, the distance to the nearest active magpie nest was found to be the most obvious factor affecting nest predation risk, among such factors as site, individual nest position, habitat type, distance to the nearest forest fragment, habitat diversity, nest concealment, distance to the nearest line habitat, and distance to a perch for avian predators. The study suggests that the spatial pattern of a dominant generalist predator can be a factor explaining the predation pattern on experimentally treated nests.
The species richness of free-living vertebrates was analysed using mapping of occurrence within individual grid squares (12 x 11.1 km) over the territory of the Czech Republic. The data on species distribution were derived from recent distributional atlases published in the last 15 years, and the records originated mostly in the last 20 years. Altogether, 384 species of cyclostomes, bony fishes, amphibians, reptiles, birds and mammals were included in this study and their presence or absence was recorded in 678 grid squares. The species numbers ascertained in the 523 grid squares situated completely within the Czech Republic varied from 92 to 259 species, with a median of 182 species. The first two principal components explained 44.9 % of the total variance and separated two main habitat gradients based on values of different environmental, topographic, and demographic variables in particular squares. The PC1 represents a gradient from urban habitats at lower altitudes to more homogenous habitats with dominant coniferous forests and meadows situated at higher altitudes. The importance of natural habitats (represented by broad-leaved and mixed forests, as well as by protected areas) and landscape heterogeneity increases along the PC2. Generalized Linear Modelling for each group of vertebrates was fitted using the number of species of individual vertebrate groups as a response variable and the first two principal components as explanatory variables. The species richness of all vertebrate groups except for reptiles is highly dependent on the PC1. The number of fish, amphibian, and bird species in squares decreases with increasing value of the PC1, i.e. it is higher in urban areas at lower altitudes. By contrast, the number of mammal species is higher in uninhabited areas at higher altitudes. The gradient represented by the PC2 is highly significant for species richness of reptiles and mammals, and the number of species of both groups increases with increasing importance of natural habitats.
A study of home range and habitat use was carried out on grey partridge (Perdix perdix) in a high density population (24–33 pairs /km2) in the south-west part of Praha, Czech Republic from 1997 to 1999. Radiotracking of individual partridge was used in the study (n = 11). Breeding period (March – June 15) and post-breeding period (June 16 – October) were analysed separately. Home range size (minimum convex polygon 95%) in the breeding period averaged 3.7 ha with a significant increase up to 8.7 ha in the post-breeding period. The majority of partridge ranges were located within dominant crop fields and idle habitats (unmanaged early stages of plant succession) referred to as weeds. Both high population density and small individual home ranges may result from the wide availability of weeds, whose attractiveness was probably due to availability of nesting sites, sufficient food supply for both partridge chicks and adults and adequate escape cover. Despite a high population density, there is an indication of little home range overlaps between pairs during the breeding period.