Intraspecific exploitation competition as a cause for density dependent breeding success in White Stork (Ciconia ciconia) was investigated. Breeding success of 101-126 pairs of White Storks was ...documented between 1999 and 2004 over an area of 1026 km2 and which included suboptimal foraging conditions. Pairs were classified in density groups according to the number of neighboring breeding pairs within their home range (i.e., within a radius of 1.5 km from the nest). The surface of potential feeding habitats was used as a food resource indicator and analyzed for all nests within the home range and compared among density groups. Breeding success was density dependent. Pairs breeding alone and pairs with one neighbor within the home range most frequently reared three chicks, pairs with two neighbors reared two, but pairs with three or four neighbors most frequently failed to raise a single chick. Regarding the use of organism-weighted densities expressed as the number of conspecific neighbors breeding within a pairs’ home range and foraging biology of the species, intraspecific exploitation competition was a possible cause for density dependent breeding success.
Abstract
The Northern Lapwing numbers across Europe are declining owing to its insufficient breeding success. To determine the size, dynamics and habitat use of the lapwing population at Dravsko and ...Ptujsko polje, a survey was carried out between 2016 and 2018. In 2016, 2017 and 2018, we recorded 148, 130, and 117 pairs, respectively. The population declined during the study and the population trend is uncertain. Approximately 12 to 21% of the national lapwing population was recorded at Dravsko and Ptujsko polje, making them one of the most important breeding areas in Slovenia. The majority of lapwings were found in bare tilled fields and fields with young spring crops that enable unbroken all-round views. Crop data analysis showed a significant preference for maize fields which are mostly bare tillage at the start of the incubation period and therefore act as an ecological trap for lapwings due to the time coincidence of the nesting period and farming operations. For the protection of the lapwing in Slovenia, we recommend a time limit of farming operations or avoiding individual nests while working in the field. Both measures are recommended to be implemented in combination with the provision of suitable foraging habitat for chicks. For greater effectiveness, we propose priority implementation of conser vation measures on traditiona l breeding sites.
Birds in agroecosystems are among the most threatened in Europe, largely due to intensification of agricultural production. For the Whinchat (Saxicola rubetra), an indicator species of high nature ...value grasslands, and whose population is decreasing over most of Europe, mowing was reported as the most significant threat several times. However, no studies to date compare mowing to other potentially significant threats to confirm this. We investigated mowing and four additional nature-related threats simultaneously and used them to construct a set of models to explain which factor has the most significant impact on Whinchat nest survival. Our study was done on a type of a grassland often found in protected areas with moderately improved production, where the density of Whinchat is high, yet influenced by human activities and natural factors. Date of mowing explained nest failure the best, followed by predation and weather, confirming mowing as the most significant problem to nest survival. Changes in mowing regime were identified as an important conservation measure. To increase breeding success of grassland birds, some of these measures (e.g., mowing postponement) were already suggested and used in EU through Agri-Environmental measures (AEM) program, but with little effect. We believe this is due to the little known indirect effects of mowing on birds during the post-fledging and pre-migration period, which is one of the least understood parts of their life cycle.
The Northern Lapwing numbers across Europe are declining owing to its insufficient breeding success. To determine the size, dynamics and habitat use of the lapwing population at Dravsko and Ptujsko ...polje, a survey was carried out between 2016 and 2018. In 2016, 2017 and 2018, we recorded 148, 130, and 117 pairs, respectively. The population declined during the study and the population trend is uncertain. Approximately 12 to 21% of the national lapwing population was recorded at Dravsko and Ptujsko polje, making them one of the most important breeding areas in Slovenia. The majority of lapwings were found in bare tilled fields and fields with young spring crops that enable unbroken all-round views. Crop data analysis showed a significant preference for maize fields which are mostly bare tillage at the start of the incubation period and therefore act as an ecological trap for lapwings due to the time coincidence of the nesting period and farming operations. For the protection of the lapwing in Slovenia, we recommend a time limit of farming operations or avoiding individual nests while working in the field. Both measures are recommended to be implemented in combination with the provision of suitable foraging habitat for chicks. For greater effectiveness, we propose priority implementation of conser vation measures on traditiona l breeding sites.
•The Scops Owl population is declining.•Main causes are linked to human activity.•Landscape dynamics reveal its potential fate.•Spatial results serve as decision support for proper environmental ...planning.
Biodiversity is declining across Europe. Modern agricultural practices, habitat fragmentation, land abandonment and climate change are key factors causing current trends in environmental change. Mobile organisms such as raptors, positioned high in the food chain, are good indicators of negative or positive landscape dynamics, since their response is fast. This assumption was tested by investigating the Scops Owl (Otus scops) population in a traditional Central European cultural landscape (Goričko Nature Park GNP) in Slovenia. The negative trend in male calling Scops Owls was correlated with static and dynamic environmental change variables derived from remotely sensed or field-based, multi-temporal data sources. Key geospatial predictors were identified and used for bird calling and breeding (C&B) suitability modelling. All geospatial models developed predicted a decline in C&B suitability (even by 33%) in almost all areas where the bird is currently active. However, the NE part of the GNP could achieve better C&B conditions for theScops Owl in the coming years (a potential 36% increase in suitability). Predictions indicate that more effort and action, to conserve the Scops Owl in the study area should be implemented in the N, NE and E part of the hilly GNP. Our results are thus highly applicable not just for decision makers in this protected area but rather in all areas across the Scops Owl’s continental population, since the methodology is easily replicable and transferable.
Abstract
In 2006–2017, annual censuses of breeding bird species regarded as indicators of natural rivers were carried out on the 38.9 km long lowland stretch of the Drava riverbed between Maribor and ...Zavrč with altered flow regime due to the operating hydropower plants. Gravel bar habitats were surveyed in four years of the study period by combining orthophoto analysis and analysis of field photographs. Effects of gravel bar management were evaluated based at 20 locations. The Little Ringed Plover
Charadrius dubius
occurred on 39.8% of the gravel bars, but most were occupied only in a few years and held just one breeding pair. Low numbers between 2009 and 2012 (< 30 pairs) were followed by a steep population increase from 2014 onwards to a maximum of 66–73 pairs (1.7–1.9 p/km). Such population dynamics was attributed to the lack of large discharges (>500 m
3
/s) and consequent overgrowing of riverbed in the first part of the study period, while the increase in the second part was due to the creation of extensive shingle areas (from 20,6 ha in 2009/10 to 37,8 ha in 2014) by the extreme flood in early November 2012, subsequent regular occurrence of large discharges outside the breeding seasons and large-scale removals of woody vegetation. Breeding population of Common Sandpiper
Actitis hypoleucos
remained at a rather similar low level (<20 p) during most of the period studied after an initial decline, and did not reflect changes in the overall surface area of riverbed habitats. Contrary to the general situation, the number of breeding pairs on gravel bars subjected to management increased several-fold. Maximum number of pairs on these bars was reached up to four years after the initiation of management measures, as only then the optimal mosaic of early successional stages interspersed with shingle areas developed at main sites. The species was widespread only on lower part of the Drava. Kingfisher
Alcedo atthis
was fairly widely distributed along the riverbed, but occurred in rather low densities throughout (c. one pair on 2–3 km of the studied riverbed on average), probably as a result of limited bank erosion and consequent overgrowing/lack of suitable nest sites. The population was estimated as stable with effects of harsh winter conditions on breeding numbers in some years. The majority of nest holes were excavated in eroded river banks along the main river channel (77.8%), followed by similar sites located in mouth areas of small tributaries of the Drava (14.8%). Regular breeding of Sand Martin
Riparia riparia
since 2012 (up to 259, mostly at only one location annually) was almost exclusively the result of the annual artificial nest site preparation programme. Fairly large gravel bar-breeding population of White Wagtail
Motacilla alba
, monitored since 2013 and predominantly ground nesting in sparsely vegetated areas, seems unusual considering the prevalent breeding habits of the species at the European scale. Conservation implications and guidelines for future management efforts are discussed.
The preference for foraging in groups and the effect of physiognomic factors of a habitat on its use by foraging Whinchats (
Saxicola rubetra
) was studied during spring migration stopover in a ...mosaic cultural landscape at the SE Adriatic coast. Every record of spatially distinct Whinchats, either a solitary individual or a group, was referred to as a Whinchat unit. The units were classified as intensively foraging, less intensively foraging or non-foraging and divided into four size classes. The effect of physiognomic habitat factors on use of habitat by foraging Whinchat units was modelled. All possible additive models using logit link function were constructed from five independent physiognomic variables: (1) natural perches (NP), (2) artificial perches (AP), (3) high herbal vegetation (HHV), (4) open bushes (OB) and (5) heterogeneity of vegetation types (HVT). Variables HHV and OB were included simultaneously in the models. Models that were substantially supported by the data were selected according to second order Akaike’s information criterion AIC
c
. Two such models contained variable(s) (1) NP and (2) NP + AP. The relative importance weights of physiognomic variables NP, AP, HVT, HHV and OB were 1, 0.38, 0.24, 0.13 and 0.13, respectively. Perches were thus the most important physiognomic habitat factor affecting habitat use by Whinchats in a mosaic cultural landscape. The great majority of Whinchats foraged in groups and the proportion of intensively foraging Whinchat units increased with unit size, leading to the conclusion that Whinchats preferred social to solitary foraging on the spring stopover at the SE Adriatic coast.
An overview of the long-term (1980–2019) population development of colonial Laridae species in continental part of Slovenia, their nest sites at anthropogenic water bodies, and various conservation ...measures with special focus on Common Tern
along the Slovenian/border part of the Drava River is given. Breeding of these species occurs only on the westernmost fringes of the Pannonian plain, on lowland floodplains of the main rivers of the Danube Basin. Altogether, breeding of Common Tern and Black-headed Gull
was recorded at 11 and 10 sites, respectively. Lake Ptuj is the single site with mixed-species colony residing there in all years of the study period, while at Ormož (two sites) it was established during the early 1990s in the Slovenian territory but moved completely to the Croatian side by the second half of the 2010s. At all other sites, a suitable breeding habitat became available or was provided by management in just a few years, or created only recently. The percentage of Common Tern national population breeding in continental Slovenia was usually well above 50% throughout the 1980s and 1990s (52–136 pairs), while in the last 16 years (77–258 pairs) it ranged between 40.8% and 69.0%. Breeding of Black-headed Gull remains largely limited to continental Slovenia. Overall, continental populations of both species in the last few years have been substantially higher compared to the most of the study period. Long-term trends were estimated as a moderate increase for Common Tern and a strong increase for Black-headed Gull. Since 2006, the Mediterranean Gull
has been a regular breeder at Lake Ptuj (up to 28 pairs), the only such site in Slovenia. Three general types of conservation measures implemented at different nesting locations are described in detail: (1) measures to create/increase the total surface of breeding habitat – the construction of new breeding structures, such as artificial islands and nesting rafts, (2) measures to maintain and enhance breeding habitat through recurring management activities, and (3) measures aimed to increase chick/nest survival and improve breeding success.
Farmland bird populations in Europe are shrinking, largely due to modern agriculture practices. In grasslands, the shift to early mowing is believed to be particularly responsible for this decline ...because it is interwoven with breeding time—a change that birds in general have not adapted to. We studied the post-fledging survival of the Whinchat, an altricial grassland passerine. Based on a sample of 74 radiotagged young Whinchats, we confirmed that they fledge at 13–15 days. Twenty-four fledged birds died, while 18 of them were depredated. The survival probability of young Whinchats, calculated using Kaplan–Meier estimates, was lowest during the first day after fledging, and slowly leveled off later. In total, the probability that a juvenile survived the first month after fledging was 0.52. During the first days after fledging, all chicks were found hiding on the ground among the grass stubble. The generalized linear mixed model predicts that half of the fledglings at 20 days old and 20% at 22 days old (8–10 days after fledging) will not escape but will instead remain still when approached by a threat. Sixteen depredations occurred during this period, all by mammal predators. Afterwards, the fledglings changed their strategy, escaping through flight. After 12 days, more and more of the chicks were found exposed on top of the grass or on the bush instead of hiding on the ground. The transition from sit and hide to escape behavior reduced the predation rate considerably. Only two chicks were depredated later, both by an avian predator. Due to the initial predator avoidance strategy, the current conservation measure (to postpone mowing until the chicks in 80% of all nests have fledged) is not sufficient to halt population decline on improved meadows. We suggest that at least 10 days more, and possibly even 14 days more, are necessary to maintain viable Whinchat populations.
In 2012 and 2013, the selection of foraging habitats and the diet of the Hoopoe Upupa epops were studied in the Goričko area, where a significant population decline of the species has been recorded ...in the past 15 years. Goričko is an area with a well-preserved traditional mosaic-like agricultural landscape very rich in biodiversity which, however, is disappearing. The diet was determined using automatic camera recordings of prey brought to chicks by parents. Mole crickets Gryllotalpa gryllotalpa were the most dominant prey (35.4% frequency and 81.3% biomass of prey), followed by Scarab beetles larvae Scarabaeidae, caterpillars Lepidoptera larvae and True flies Diptera. Feeding frequency was highest in the period of most intensive chick growth (between 8 and 21 days of age). Selection of foraging habitat was researched by observation of birds during foraging. Hoopoes foraged mostly in mown meadows and grassy courtyards and, to a lesser extent, on sandy cart tracks and road edges. These habitats were characterized by low vegetation and patches of bare ground that enabled Hoopoes to forage efficiently. Home range size was determined using minimum convex polygons. The maximum home range size was between 42.9 and 57.7 ha, while the percentage of foraging habitats within the home range did not exceed 18%. Based on our results, we propose the following measures for effective Hoopoe conservation in the area: maintaining the present range of existing unimproved meadows, stopping the conversion of meadows into fields, restoring fields to meadows, prohibiting the use of pesticides targeting Mole crickets.
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