Nest Destruction Research Articles

Do voles make agricultural habitat attractive to Montagu's HarrierCircus pygargus?

Loss and degradation of habitat threatens many bird populations. Recent rural land‐use changes in the Netherlands have led to a shift in habitat use by breeding Montagu's HarriersCircus pygargus. Since the 1990s, unprecedented numbers of this species have bred in farmland compared with numbers in natural habitat. Destruction of nests by agricultural operations, however, compromises breeding success. Between 1992 and 2005, the number of breeding pairs in the northeastern Netherlands was positively, though weakly, correlated with previous‐year estimated abundance of voles, mostlyMicrotus arvalis. In good vole years, the onset of laying was earlier and mean clutch size was larger. Vole abundance was relatively higher in set‐aside land and in high and dense vegetation. We suggest that agri‐environmental schemes aimed at increasing the availability of voles in agricultural breeding areas may be an effective management tool for the conservation of Montagu's Harriers in the northeastern Netherlands.

Influence of Land Use on Mallard Nest-Structure Occupancy

We investigated the relationship between land use and mallard (Anas platyrhynchos) occupancy of single- and double-cylinder nest structures on a 658-km2 (254-mile2) western Minnesota, USA, study area from 1997–1999. We used hierarchical logistic regression to spatio-temporally model structure occupancy as a function of land use, number of nearby structures, number of mallard pairs with access to the structure, size of the open-water area including the structure, and structure type. We fit models to data from 4 different-sized buffers around each structure to investigate scale influences. Goodness-of-fit, predictive ability, and amount of reduced spatio-temporal correlation were similar for each buffer-size model. We made inferences using the 1.6-km-radius buffer model because it produced the lowest deviance. The amount and attractiveness of nesting cover (i.e., as indexed by visual obstruction measurements [VOMs]) within a buffer interacted with nest-initiation period (P = 0.003). The VOMs and nest occupancy were positively associated early in the nesting season, but the pattern reversed later in the nesting season. Structure occupancy and area of open water around a structure were related quadratically (P = 0.004), with odds of a structure in median-sized open-water areas being occupied increasing until the open-water area was ~16 ha. Year and nesting-season period interacted (P = 0.002), reflecting different nest-initiation phenology. Number of pairs with access to a structure had no effect on nest initiations (P = 0.7), perhaps due to our inability to account for within-season changes in pair numbers. Number of nearby structures (P = 0.8) was unrelated to initiation probability, but structure density was low (0.05/km2). We suspect that mallard settling patterns and an unmeasured temporal relationship between VOMs and numbers of pairs with access to structures produced the VOM × period interaction. Structures deployed in larger open-water areas where surrounding residual upland cover is abundant can improve mallard nest success early in the nesting season when duckling survival is the greatest and can reduce hen mortality associated with nest destruction and re-nesting.

Evaluation of density-dependent processes and green turtle Chelonia mydas hatchling production at Tortuguero, Costa Rica

The role of density-dependent processes in sea turtle populations remains largely unknown. This study quantified density-dependent and density-independent processes that underlie hatchling production in the green turtle nesting population at Tortuguero, Costa Rica, and estimated current mean hatchling output and potential carrying capacity of Tortuguero beach for hatchlings and nesting females. Density-dependent effects of nest destruction by nesting females and coatis were evaluated in the 2000 nesting season along the 28.8 km nesting beach. To quantify factors affecting hatchling production, the fates of nests were monitored in twelve 50 m long study plots. Density-dependent factors included nest destruction by nesting females and predation by coatis, whereas density-independent factors included beach erosion, beach flooding, and below-beach- surface destruction by crabs, ants, microbes, and plant roots. Calculations indicated that between 5 and 6 million hatchlings are currently produced, while a simulation model suggested that at carrying capacity, 6 to 10 times as many hatchlings could be produced by more than 600 000 nesting females. The current mean number of females nesting at Tortuguero is between 3 and 4% of the population that is estimated to nest at carrying capacity. This estimate is consistent with previous estimates that modern day populations of Caribbean green turtles represent only 3 to 7% of pre-exploitation levels. The hatchling production model is applicable to other beaches and sea turtle species, and provides a framework to evaluate recovery goals for sea turtles.

NEST DESTRUCTION ASSOCIATED WITH MORTALITY AND DISPERSAL OF BURROWING OWLS IN THE IMPERIAL VALLEY, CALIFORNIA

Abstract We documented the effects of inadvertent nest destruction from road maintenance activities on the survivorship, reproductive success, and breeding dispersal of burrowing owls (Athene cunicularia) breeding in natural burrows along the water delivery system in the Imperial Valley of California. The activities affected 4 nests (7 adult owls) along an 800-m section of road, filling in or destroying all of the burrows. Three of 7 adult owls in the impacted area were killed, 2 of 2 active nests failed, 2 nests that had previously failed were destroyed and might have led to the dispersal of the surviving adults. We suggest that artificial burrows will reduce the conflict between maintenance and burrowing owl nests, which will benefit both owls and landowners.

Breeding success of a colony of Boat-billed Herons Cochlearius cochlearius (Ciconiiformes: Ardeidae) in pasturelands of Costa Rica

The breeding success of a double-brooding colony of Boat-billed Herons Cochlearius cochlearius was studied in pasturelands of Costa Rica. Mean clutch size in the first clutches (2.9 eggs/nest) was higher than in second and repeat clutches (2.3 eggs/nest). Breeding success was similar in the first attempt and second attempts (20.7 % and 21.7 %, respectively). In both attempts earlier nests enjoyed a higher breeding success. Starvation of the youngest chicks within the nest and destruction of nests by bad weather conditions were the main factors related to nestling death. No effects of human activity on the reproduction of the breeding colony were observed.

An alternative strategy for maintenance of eusociality after nest destruction: new nest construction in a primitively eusocial wasp

Although nests are central to colonial life in social insects, nests are sometimes damaged by predators or natural disasters. After nest destruction, individuals usually construct new nests. In this case, a sophisticated mechanism like the scent trail pheromone used in large insect colonies that recruit individuals to new nest sites would be important for the maintenance of eusociality. In independent-founding Polistes wasps, it is well known that queens enforce workers physiologically on the natal nests even if evidence of trail pheromone use has not been exhibited. We investigated the effect of the queen on an alternative strategy for the maintenance of eusociality by first females after nest destruction in the primitively eusocial wasp Polistes chinensis. We predicted that the first females in queen-absent colonies have various behavioral options after nest destruction. Even if the females construct new nests cooperatively with other individuals, the new nest construction should be conducted more smoothly in queen-present colonies because the queens regulate the behavior of wasps. We made wasps construct new nests by removing the entire brood from existing nests. The presence of the queen did not cause variation in the alternative strategy of the first females, as the first females (workers) usually constructed new nests cooperatively irrespective of the queen-presence. Thus, the workers in the queenpresent colonies affiliated to the new nest construction more smoothly and constructed new nests more efficiently than workers in the queen-absent colonies. Our results suggest that the presence of the queen is important for maintaining eusociality in primitively eusocial wasps after nest destruction.

Preference by <I>Vespula germanica</I> (Hymenoptera: Vespidae) for Processed Meats: Implications for Toxic Baiting

The German yellowjacket, Vespula germanica (F.) (Hymenoptera: Vespidae), was introduced into Australia in 1959 and has established throughout southern Australia. In urban environments, V. germanica is frequently a nuisance pest at public gatherings and to homeowners. In native environments, it has the potential to pose a threat to native invertebrates. The current practice for controlling the wasps is nest destruction with pesticide. However, locating the nest(s) is not always practical or possible. Meat baits impregnated with an insecticide that foraging wasps cut and carry back to the nest offer a means of suppressing wasps where the nest sites are unknown. The success of meat baits depends on the attractiveness and acceptance of the meat to the wasp and the mode of action of the insecticide. Our objective was to determine wasp preference and acceptance of five processed meats: canned chicken or fish and freeze-dried chicken, fish, or kangaroo. We found that more wasps visited and took freeze-dried kangaroo and canned chicken than the other baits. Canned and freeze-dried fish were similarly preferred, and freeze-dried chicken was the least attractive and accepted by foraging wasps. Our findings demonstrate that wasps prefer some processed meats and hence take more loads back to the nest. By combining a suitable insecticide with a meat bait preferred by wasps, the likelihood of effective suppression of nuisance wasp populations should be increased.

Impact of density‐dependent nest destruction on emergence success of Guianan leatherback turtles (Dermochelys coriacea)

AbstractTo assess the impact of nest covering on a leatherback turtle Dermochelys coriacea nesting beach in French Guiana, we used field study data and a modelling approach. Field results showed that the covering of a pre‐existing nest by a new one causes the destruction of the older nest under some conditions of time and covering area, and almost always causes the destruction of the new nest. We then used field results to parameterize a theoretical model of the nesting beach. This allowed us to obtain a ‘critical carrying capacity for the beach’: the number of nests deposited for which the number of successful nests is maximum; when this number increases, the number of successful nests decreases. With these results, we then concluded that density‐dependent nest destruction plays a role in the functioning of the nesting beach. These results are essential for our understanding of nest‐site selection at the scale of the beach and its consequences.

Viability of the Endangered Little Bustard Tetrax tetrax Population of Western France

Stochastic computer simulations are used to evaluate the sensitivity of Little bustard population parameters, estimating the survival probabilities of the seven endangered Little bustard populations of central-western France for which conservation actions are currentlybeing or have been implemented. Different scenarios of parameter compensation for those nuclei to establish parameter levels assuring population viability are discussed. Adult survival, productivity per female, initial population size and carrying capacity were the most sensitive parameters in a hypothetical, isolated population. Juvenile survival also affected population survival, although its sensitivity was lower. Sex ratio did not have a linear effect on population survival, but probability of extinction increased for extreme values. Productivity per female and initial population size, varied strongly among the populations studied, determining their average time of extinction and growth rate. When a metapopulation scenario was simulated, the survival probabilities of each population and the metapopulations stayed close to 1.0 if no mortality was associated to migration. When mortality during migration was included in the simulations, the metapopulation's probability of survival significantly decreased under 90%. This approach may help managers to correctly address conservation measures and design effective strategies, which should be directed mainly to improve productivity, enhance female survival, and minimise mortality during migration (e.g. promoting insect-rich nesting substrates, avoiding female killing and nest destruction at harvesting, reducing the risk of collision with powerlines, or controlling poaching).

Malacosoma parallela

<i>Malacosoma parallela</i>

Exploitation competition between hole‐nesters ( Muscardinus avellanarius , Mammalia and Parus caeruleus , Aves) in Mediterranean woodlands

Data from a long-term study (1993–2003) using artificial nest-boxes, were analysed to examine competition for nesting between blue tit Parus caeruleus and common dormouse Muscardinus avellanarius in Sicily. Occupation rates and the reproductive biology of the blue tit in sample woodlots outside the distribution area of the common dormouse were used as a control in sample areas where the two species were syntopic. A selection test showed that the two species, when living in syntopy, actively chose the small nest-boxes, thus overlapping in the use of the same spatial resource. The experimental exclusion of the common dormouse from nest-boxes caused an increase of blue tit occupation rate. Once the effect of nest-box density was removed, complementary density changes between the two species clearly appeared. The population cycle of both species in the areas of syntopy showed a swinging pattern, i.e. in areas or during years of common dormouse high abundance few blue tits bred and vice versa. The abundance of the blue tit was affected not only by common dormouse abundance, but also by some habitat and climate variables. Blue tits had low breeding success and a high percentage of nest failure (38% in syntopy vs 3% in control areas), owing to nest destruction and predation by common dormouse, as well as probably also by other rodents (23%) and Martes martes (15%). Another experiment, using stuffed models, showed that the blue tit recognized the common dormouse as an enemy, and behaved as if confronted by a competitor or predator species to protect their nests.

Modelling population reinforcement at a large spatial scale as a conservation strategy for the declining little bustard (Tetrax tetrax) in agricultural habitats

The little bustard (Tetrax tetrax) has declined rapidly across European farmland landscapes due to agricultural intensification. In France, the number of breeding males in agricultural habitats has been reduced by 92% over the last 20 years as a result of decreases in insect abundance and nest destruction during harvesting. An age- and sex-structured stochastic metapopulation model was formulated for the remaining little bustard population in south-west France and, using actual estimates of demographic rates obtained after 1997, its extinction risk over the next 30 years was estimated to be ca. 0.48. Limited population reinforcement has thus appeared as a potential conservation strategy for this species in agricultural habitats, while agro-environmental actions have begun to have an effect on habitat quality at the landscape level. Different strategies for the reinforcement of fledglings, including the number and frequency of releases and the number of release localities in relation to four criteria for choosing the release points, were evaluated in terms of their effect in reducing the extinction risk of local populations and of the metapopulation. The reinforcement of 100 fledglings per year for 5 years and choosing the actual release points using the current abundance were found to be the optimal choices for reducing the estimated extinction risk of the remaining little bustard population in south-west France.

Key issues in assessing the feasibility of reintroducing the great bustard Otis tarda to Britain

The great bustard is a globally-threatened species needing conservation action across Europe. This paper discusses key issues in the case for reintroducing the bird to Britain. Great bustards became extinct as a breeding species in Britain in 1832 probably as a result of hunting, agricultural change and inclement weather. The factors that caused the loss are no longer thought to operate. Suitable habitat exists in pockets across England and especially on Salisbury Plain where a large area is protected for military training and conservation purposes. The Plain combines short grass areas for lekking, long grassland for feeding and adjacent arable land for nesting. Pilot studies on arthropods in long grassland suggest that their density is sufficient for chick-rearing but the precautionary creation of additional food-rich areas among arable crops is recommended. Genetic studies indicate that Britain's bustards probably belonged to the central European group and that restocking should not use birds from Iberia. Only Russia has sufficient birds to supply a reintroduction project and losses there through nest destruction are high. By rescuing eggs, artificially incubating them and transporting chicks to Britain, the project should have zero detriment to the donor population. Modelling indicates that 40 chicks will need to be brought to Britain for 5–10 years to build a founder population of 100 birds. Although focused on direct action in Britain, the project will promote grassland conservation across Europe and serve as a model for translocating bustards elsewhere.

Southern marl prairies conceptual ecological model

About 190,000 ha of higher-elevation marl prairies flank either side of Shark River Slough in the southern Everglades. Water levels typically drop below the ground surface each year in this landscape. Consequently, peat soil accretion is inhibited, and substrates consist either of calcitic marl produced by algal periphyton mats or exposed limestone bedrock. The southern marl prairies support complex mosaics of wet prairie, sawgrass sawgrass (Cladium jamaicense), tree islands, and tropical hammock communities and a high diversity of plant species. However, relatively short hydroperiods and annual dry downs provide stressful conditions for aquatic fauna, affecting survival in the dry season when surface water is absent. Here, we present a conceptual ecological model developed for this landscape through scientific concensus, use of empirical data, and modeling. The two major societal drivers affecting the southern marl prairies are water management practices and agricultural and urban development. These drivers lead to five groups of ecosystem stressors: loss of spatial extent and connectivity, shortened hydroperiod and increased drought severity, extended hydroperiod and drying pattern reversals, introduction and spread of non-native trees, and introduction and spread of non-native fishes. Major ecological attributes include periphyton mats, plant species diversity and community mosaic, Cape Sable seaside sparrow (Ammodramus maritimus mirabilis), marsh fishes and associated aquatic fauna prey base, American alligator (Alligator mississippiensis), and wading bird early dry season foraging. Water management and development are hypothesized to have a negative effect on the ecological attributes of the southern marl prairies in the following ways. Periphyton mats have decreased in cover in areas where hydroperiod has been significantly reduced and changed in community composition due to inverse responses to increased nutrient availability. Plant species diversity and community mosaics have changed due to shifting gradients to more terrestrial or more aquatic communities, displacement of native communities by non-natives, expansion of woody plants, high-intensity dry season fires, tree-island burnout, and reduced microtopography resulting from alligator population decline. Cape Sable seaside sparrow populations are threatened by nest destruction resulting from extended hydroperiods, drying pattern reversals, and high intensity dry season fires, as well as by the expansion of woody plants into graminoid wetland habitats. Populations of marsh fishes and associated aquatic fauna that constitute the aquatic prey base for higher vertebrates have decreased in density and changed in species composition and size structure due to loss of wetland spatial extent, shortened hydroperiod, increased drought severity, loss of aquatic drought refugia in solution holes and alligator holes, and spread of exotic fishes. American alligator populations have declined in the Rocky Glades, and alligator holes have filled with sediment, as a result of shortened hydroperiod and increased drought severity. Habitat options for wading birds to forage during the early dry season and during unusually wet years have been reduced due to loss of spatial extent and shortened hydroperiod.

Predicting short-term extinction risk for the declining Little Bustard ( Tetrax tetrax) in intensive agricultural habitats

Populations of Little Bustard ( Tetrax tetrax) have shown pronounced declines in European farmland landscapes over the last 25 years due to the intensification of agricultural practices. In France, the number of breeding males in agricultural habitats has declined by 92% since 1980 as a result of decreases in insect abundance and nest destruction during harvesting. We formulate an age- and sex-structured stochastic model for the remaining Little Bustard population in SW France that has been studied since 1997 and, using actual values of demographic rates, we estimate its extinction risk over a time period of 30 years to be of 0.45. At the level of local populations, the extinction risk ranged between 0.66 and 0.90, largely depending on the initial population size and local fecundity of each population. A comprehensive sensitivity analysis evaluated the influence of uncertain demographic rates and of aspects of the spatial dynamics (sex and age dispersing individuals, sex-biased dispersal and different dispersal rates) on the predicted extinction risks and showed that our model was robust to changes of a wide range of combinations assessed. Given the severity of the current decline, and the spatial issues raised by our analysis, implications of our findings for the conservation of this endangered species are suggested.

Effects of wave action on nesting activity in the littoral five-spotted wrasse, &lt;i&gt;Symphodus roissali&lt;/i&gt;, (Labridae), in the northwestern Mediterranean Sea

The nesting activity of the littoral five-spotted wrasse, Symphodus roissali, was investigated near Blanes (northwestern Mediterranean Sea). Males construct and defend several nests over the entire reproductive period while females spawn asynchronously in these nests. Nesting activity continued from around the end of March to the end of June in the case of the study population. Nesting intensity, nesting success and nest destruction varied between years and sites. Differences between the numbers of nests that survive the nesting cycle and those that are destroyed can be related to environmental conditions, primarily wave height. Sufficiently protracted periods (> 1 week) of favourable sea conditions allow nests to survive and complete their cycle.

Abundance and Projected Control of Invasive House Crows in Singapore

The Indian house crow (Corvus splendens) has successfully invaded tropical and subtropical regions well beyond its native range, reaching pest proportions in many areas. The invasive population of house crows in Singapore (Southeast Asia) has increased at least 30-fold since 1985 and now numbers in excess of 130,000 birds. To understand the population ecology and behavior of the house crow in Singapore, we undertook regular population size and roost surveys, dissections of birds shot (to provide age structure and breeding status), detailed nestsite observations, and monitoring of coastal dispersal. Using a discrete-time, density-dependent population model to synthesize this information, we demonstrated that at least 41,000 crows will need to be culled in the first year of a control program, and equivalent effort committed each year thereafter, to be confident of suppressing the Singapore population from its 2001 density of 190 birds/km(2) to the management target of <10 birds/km(2) within a 10-year period. This figure drops to 32,000 if culling is combined with other management strategies such as resource limitation and nest destruction. Complete eradication of the house crow from Singapore may be an unrealistic goal due to potential difficulties in detecting crows at IOW population densities and influx of migrants from neighboring Malaysia. Our study has implications for pest-bird management in other cities in Asia, Africa, and the Middle East, and presents it surrogate population-dynamics management tool for use in regions where the house crow has become established as a pest species, but where limited local field data is available.

Does Removal of Duck Nest Predators Affect the Temporal Patterns of Predation for Simulated Nests of Grassland Songbirds?

We tested whether the temporal patterns of songbird nest predation changed following removal of predators of duck nests in North Dakota, USA, 1995-1996. Overall, 2286 simulated nests were deployed of which 951 were equipped with depredation timing devices that recorded the time of day of nest destruction. Predators destroyed 242 timer nests, and 155 depredation events were recorded. Temporal distribution of predation events was uniform over a 24-h period. However, predator groups, identified by using marks left on modeling clay eggs, depredated nests at different times. Mean times of depredation were 07h41, 12h57, 17h50, and 22h47 for small mammals, ground squirrels, birds, and medium-sized mammals, respectively. Daily depredation events occurred earlier on removal versus non-removal sites. However, within each predator group, there was no difference in depredation times between removal and non-removal sites. We suggest that the difference in time of depredation is caused by the differential importance of each predator group on removal versus removal sites, and thus conclude that removing duck nest predators does not affect temporal foraging patterns of smaller predators.

Nest Predation as a Limiting Factor to the Breeding Population Size of the Collared FlycatcherFicedula albicollisin the Białowieża National Park (NE Poland)

Abstract. This study is based on an analysis of nest-histories of 652 Collared Flycatcher nests found in natural tree cavities in the Bialowieza National Park in 1988–1999. The secondary-cavity-nester Collared Flycatcher constitutes migratory single-brooded population breeding in high density in the primeval oak-lime-hornbeam (Querco/TillioCarpinetum) stands. Nest predation was the main reason of the breeding losses (240 nests) accounting for 91% (82%–100%) of them. Local production of fledglings was affected by nest predation caused by rodents, mustelids and Great Spotted Woodpecker. In this study a link between forest rodent cycles and the Collared Flycatcher fluctuations in number was documented. Number of produced fledglings depended on both, positively the number of the Collared Flycatcher breeding pairs in year N and negatively on the Yellow-necked Mouse density in year N. Rate of nest destruction is related to the density of the Yellow-necked Mouse recorded in BNP, while independent on the Collared...

Hen harrier foraging success in relation to land use in Scotland

AbstractIn the UK, hen harriers (Circus cyaneus) are illegally killed on moorland that is managed for red grouse (Lagopus lagopus scoticus), and they produce fewer young per female on grouse moorland than on either unmanaged moorland or forestry. However, those breeding attempts on grouse moorland that escape nest destruction produce more young than in other land‐use classes. One explanation for this difference is that food is more available to harriers on managed moorland than elsewhere. To examine this hypothesis, we compared the capture rates of hunting male harriers on sites across Scotland. Four of these sites were managed for grouse whilst the remaining three consisted of either unmanaged moorland or a mixture of unmanaged moorland and young forestry plantations. We found a significant difference in capture rates, with harriers on managed grouse moorland capturing prey at a greater rate than elsewhere, supporting the idea that prey were more available on grouse moorland. However, there was no difference in strike rates between the land‐use classes, suggesting that prey were not necessarily more abundant on grouse moors. Males on unmanaged moorland tended to catch larger prey, though this was insufficient to compensate fully for the reduced capture rates. The improved hunting success on grouse moorland means that this habitat is likely to be more attractive to breeding harriers, thereby increasing the conflict between those interested in maximizing grouse numbers and those interested in conserving rare raptors.