Western Range Limit Research Articles

Checklist of Odonata of Sidi Bel Abbes, Northwest Algeria

The odonates of Algeria have been studied for more than a century and a half, but the Northwestern part of the country has historically received little attention. A recent study in central North Algeria reported a species new to the country, suggesting that new investigations in unexplored areas are necessary to fully understand the local odonatofauna. We studied assemblages of odonates in 23 sites in Sidi Bel Abbes (Northwest Algeria) by bimonthly recording adults across a 200 m-transect from May to August of 2019–2022. Our sampling yielded 29 species (13 damselflies and 16 dragonflies) belonging to 19 genera and seven families. We recorded a new locality for the regionally endangered Coenagrion mercuriale, expanding the western range limit of the species in Algeria. We documented the occurrence of Selysiothemis nigra, a species that has recently become more frequent in North Africa. Ischnura pumilio and Onychogomphus forcipatus unguiculatus, which are relatively rare in the region, were also recorded. The arid-dwelling Trithemis kirbyi and the Mediterranean endemic Orthetrum nitidinerve were quite common in the study area. This study fills an important gap of knowledge in our understanding of odonate geographic distribution in North Africa.

Allele Surfing and Holocene Expansion of an Australian Fig (Ficus—Moraceae)

The creek sandpaper fig of southeastern Australia, Ficus coronata Spin, is culturally significant to Australian traditional owners who made use of the leaves to smooth timber and ate the fruit. The species is thought to have a long history on the continent, with some suggesting a Gondwanan origin. However, distributional patterns and overall ecology suggest a recent expansion across suitable habitats. We used landscape genomic techniques and environmental niche modelling to reconstruct its history and explore whether the species underwent a recent and rapid expansion along the east coast of New South Wales. Genomic analysis of 178 specimens collected from 32 populations throughout the species’ New South Wales distribution revealed a lack of genetic diversity and population structure. Some populations at the species’ southern and western range limits displayed unexpected diversity, which appears to be the result of allele surfing. Field work and genetic evidence suggest a Holocene expansion which may have increased since European colonisation. We also present a novel method for detecting allele surfing—MAHF (minor allele at highest frequency).

ClimPlant: Realized climatic niches of vascular plants in European forest understoreys

AbstractMotivationDetailed knowledge on the climatic tolerances of species is crucial to understand, quantify and predict the impact of climate change on biodiversity and ecosystem functions. However, quantitative data are limited; often, only expert‐based qualitative estimates are available. With the ClimPlant database, we capitalize on the link between species distribution ranges and macroclimate to infer the realized climatic niches of 968 European forest plant species.Main types of variables containedThe ClimPlant database contains information on the distribution of monthly, growing‐season and annual mean, minimum and maximum temperature and total precipitation within the distribution range of 968 European forest plants.Spatial location and grainEurope in 10 arc‐min grid cells; the study area has been cropped rectangularly at 15° W (Atlantic Ocean), 60° E (Ural Mountains), 25° N (Sahara) and 75° N (Arctic Ocean).Time period and grainThe distribution ranges of forest plant species are based on two renowned distribution atlases. The monthly mean, minimum and maximum temperature and precipitation between 1970 and 2000 were extracted from WorldClim v.2.Major taxa and level of measurementNine hundred and sixty‐eight vascular plant species of European forests, with taxonomy following the Euro+Med PlantBase nomenclature .Software formatData in 56 CSV files, with 1,000 values for monthly, growing season and annual observations of mean, minimum and maximum temperature and precipitation in the distribution range for every species. One summary CSV file with summary statistics (mean, median, fifth and 95th percentile), for every species, of each climatic variable, together with seven key geographical descriptors: area of the distribution range, latitude and longitude of the centroid, and northern, eastern, western and southern range limits within the study area.

Remnant American Chestnut (Castanea dentata) Near the Historical Western Range Limit in Southwestern Tennessee

The American chestnut (Castanea dentata) was once widespread in eastern North America and an ecologically important hardwood tree of deciduous forest communities prior to its near-eradication by chestnut blight (Cryphonectria parasitica). Remnant populations occur across much of its historical range, especially in older forests of the Appalachians and northeastern U.S. However, broad swaths of the southwestern portion of the species' historical range remain poorly documented, potentially limiting the representation of genetic variation important for local adaptation in restoration efforts. Ongoing discovery and life-history characterization efforts for remnant C. dentata remains a priority to better understand the distribution and ecological status of this once important species, while identifying potential genetic sources of locally adapted or blight resistant trees. Here, we report the discovery of 22 C. dentata at four sites in southwestern Tennessee, adding novel observations that extend the range of known extant occurrences to the extreme western edge of the historical distribution in Fayette County. These observations include potentially reproductive individuals that should be revisited to assess reproductive and blight status, and that should be evaluated for current germplasm collection and restoration efforts.

First Report of <i>Pseudorhombus diplospilus</i> (Pleuronectiformes: Paralichthyidae) from East Coast of India

A large-tooth flounder, Pseudorhombus diplospilus Norman (1927) (Pleuronectiformes: Paralichthyide), is reported from east coast of India based on a single specimen collected from Royapuram fishing harbor, Chennai, Tamil Nadu with detailed meristic and morphometric study. This forms the ninth species in the genus Pseudorhombus and the second species in having palmate gill rakers from Indian waters. With this report of P. diplospilus, its western limit of distributional range is extended from Indonesia and west Australia to east coast of India.

Assessing the environmental and dispersal controls onFagus grandifoliadistributions in the Great Lakes region

AbstractAimThis paper assesses the relative importance of environmental filtering and dispersal limitations as controls on the western range limit ofFagus grandifolia, a common mesic late‐successional tree species in the easternUnited States. We also test for differences in species–environment relationships between range‐edge populations ofF. grandifoliain eastern Wisconsin and core populations in Michigan. Because environmental conditions between the states differ moderately, while in Michigan dispersal presumably no longer limitsF. grandifoliadistributions,F. grandifoliaoffers a classic case study for biogeographers, foresters, and palaeoecologists interested in understanding processes governing species range limits.LocationWisconsin and Michigan,USA.TaxonFagus grandifolia.MethodsThis study combines historical datasets ofF. grandifoliafrom the Public Land Survey, environmental covariates from soil maps and historical climate data, three spatial scenarios of dispersal limitation, and five species distribution models (SDMs). We test dispersal limitation and environmental filtering hypotheses by assessingSDMtransferability between core and edge populations, measuring the importance of dispersal and environmental predictors, and using a residual autocovariate model to test for spatial processes not represented by these predictors.ResultsFagus grandifoliapresence was best predicted by total snowfall in Michigan and by dispersal, summer precipitation, and potential evapotranspiration (PET) in Wisconsin. Following the addition of dispersal as a predictor, most Wisconsin models improved and spatial autocorrelation effects largely disappeared. Transferability between core and edge populations was moderate to low.Main conclusionsBoth environmental and dispersal limitations appear to govern the western range limit ofF. grandifolia. Species–environment relationships differ between range‐edge and core populations, suggesting either stronger environmental filtering at the range edge or fine‐scale, spatially varying interactions between environmental factors governing moisture availability in core populations. Although lakes, like Lake Michigan, both moderate regional climates and act as dispersal barriers, these effects can be disentangled through the joint analysis ofSDMs and historic observational datasets.

Experimental test of assisted migration for conservation of locally range-restricted plants in Alberta, Canada

Given projected rates of climate change, species with limited dispersal may be unable to migrate at the pace necessary to maintain their current climate niches. This could lead to increased risk of extirpation or extinction, especially for locally range-restricted species within fragmented landscapes. Assisted migration has been suggested as a proactive conservation tool to mitigate these risks. We tested assisted migration for Liatris ligulistylis and Houstonia longifolia, two perennial forbs considered ‘vulnerable’ and ‘imperilled’, respectively, in Alberta, Canada, where they are at their northern and western range limits. Both mature plants and seeds were translocated to replicate sites at four geographic locations along a north-south gradient representing the current ranges of the species (central) and areas south (warmer) and north (cooler) of their current range. L. ligulistylis adult plants thrived ∼500 km north of the species current range with survival, growth, and flowering similar to or exceeding performance in the current range, the influence of soil was also tested by comparing the performance of transplanted mature plants in soil from the source location versus the translocation (recipient) site. Plants planted into soil from the source location had increased flower bud production at all sites. Seedling establishment was significantly higher at sites north of the current range, but much lower in the southern locations. These results suggest that L. ligulistylis is in climate disequilibrium, potentially due to migration lags, and that it might be vulnerable to near-future climate vulnerability. For H. longifolia, the influence of flower morph type and location were tested. Only 8 out 130 translocated adult plants survived, five with thrum flowers and three with pin flowers; no seedling establishment was observed in the first growing season, which experienced drier than normal conditions. Among the eight adult plants, seven survived in the central location and one in the north demonstrating specific habitat requirements and conditions that may make this species difficult for translocation and establishment. Overall, locally rare and range-restricted plants with limited dispersal demonstrate climate sensitivity to current conditions and potential for assisted migration, yet species-by-species testing is needed to understand vulnerability and efficacy of this approach.

Warming drives a front of white spruce establishment near western treeline, Alaska.

Regional warming has led to increased productivity near the boreal forest margin in Alaska. To date, the effects of warming on seedling recruitment have received little attention, in spite of forecasted forest expansion. Here, we used stand structure and environmental data from 95 white spruce (Picea glauca) plots sampled across a longitudinal gradient in southwest Alaska to explore factors influencing spruce establishment and recruitment near western treeline. We used total counts of live seedlings, saplings, and trees, representing five life stages, to evaluate whether geospatial, climate, and measured plot covariates predicted abundance, using current abundance distributions as a surrogate for climate conditions in the past. We used generalized linear models to test the null hypothesis that conditions favorable for recruitment were similar along the environmental gradient represented by longitude, by exploring relationships between per-plot counts of each life stage and the covariates hypothesized to affect abundance. We also examined the relationship between growing degree days (GDD) and seedling establishment over a period of three decades using tree-ring chronologies obtained from cores taken at a subset of our sites (n=30). Our results indicated that seedling, sapling, and tree abundance were positively correlated with temperature across the study area. The response to longitude was mixed, with earlier life stages (seedlings, saplings) most abundant at the western end of the gradient, and later life stages (trees) most abundant to the east. The differential relationship between longitude and life-stage abundance suggests a moving front of white spruce establishment through time, driven by changes in environmental conditions near the species' western range limit. Likewise, we found a positive relationship between periods of seedling establishment and GDD, suggesting that longer summers and/or greater heat accumulation might enhance establishment, consistent with the positive relationship we found between life-stage abundance and temperature.

The Distribution, Population Status, and Wildlife Product Trade of Himalayan Musk Deer in Gilgit-Baltistan, Pakistan

Himalayan musk deer (Moschus chrysogaste leucogaster) is an IUCN Red List Endangered species that reaches its western range limit in Pakistan, although its distribution or population size is unknown. Here, we mapped its distribution, described habitat preferences, estimated population sizes, recruitment and mortality, and reported the market values of musk deer wildlife products. We used two approaches: analyzing local wisdom (traditional ecological knowledge) through the use of questionnaires, and conducting confirmatory field surveys of selected areas. Questionnaire respondents indicated musk deer sightings in 28 of 84 localities; mainly in Himalayan dry temperate forests with >20% forest cover. There were an estimated 224-363 individuals. When females were observed with offspring, there were often two fawns present, suggesting twinning. Hunting appears largely opportunistic, with approximately 20% of the population killed each year. Musk, skins and canine teeth are sold in markets. Future threats include future human population growth, growing awareness about musk deer product values and political instability.

Assessment of Chosen Reproductive Cycle Processes and Genetic Diversity ofSalix myrtilloidesL. in Wetlands of Polesie Lubelskie: The Prospects of Its Survival in the Region

ABSTRACT Salix myrtilloides L. is an endangered species whose western limit of range runs through Poland. The main aim of the study was to increase the knowledge on the ecology and biology of S. myrtilloides populations in the Polesie Lubelskie region (Eastern Poland) in order to create an effective protection program. An 80% decrease in its population was found in this area. Our study was conducted to identify the mechanisms responsible for the process of withdrawal of this species from its natural stands by determining whether the processes of generative reproduction (pollen viability and germinability, seed germination ability and dynamics) in the populations occur properly and by characterizing within- and among-population genetic diversity of S. myrtilloides, using ISSR (Inter-Simple Sequence Repeat) primers. The results confirmed that S. myrtilloides pollen viability was high (84.17±8.67), and so were the seed germination ability (76% of the total number of sown seeds/24 h) and dynamics. The within-...

Modeling the Present and Future Geographic Distribution of the Lone Star Tick, Amblyomma americanum (Ixodida: Ixodidae), in the Continental United States.

The Lone star tick (Amblyomma americanum L.) is the primary vector for pathogens of significant public health importance in North America, yet relatively little is known about its current and potential future distribution. Building on a published summary of tick collection records, we used an ensemble modeling approach to predict the present-day and future distribution of climatically suitable habitat for establishment of the Lone star tick within the continental United States. Of the nine climatic predictor variables included in our five present-day models, average vapor pressure in July was by far the most important determinant of suitable habitat. The present-day ensemble model predicted an essentially contiguous distribution of suitable habitat extending to the Atlantic coast east of the 100th western meridian and south of the 40th northern parallel, but excluding a high elevation region associated with the Appalachian Mountains. Future ensemble predictions for 2061-2080 forecasted a stable western range limit, northward expansion of suitable habitat into the Upper Midwest and western Pennsylvania, and range contraction along portions of the Gulf coast and the lower Mississippi river valley. These findings are informative for raising awareness of A. americanum-transmitted pathogens in areas where the Lone Star tick has recently or may become established.

Role of forest fires in Holocene stand-scale dynamics in the unmanaged taiga forest of northwestern Russia

Fossil pollen, conifer stomata, and charcoal records for the last 10,000 years were studied from three small hollow sites (Larix Hollow, Mosquito Hollow, and Olga Hollow) located at the modern western range limit of Siberian larch ( Larix sibirica) in northwestern Russia to investigate the role of forest fires in stand-scale dynamics of taiga vegetation. Wavelet coherence analysis was utilized to reveal the significance of fire on the vegetation composition at different timescales by assessing the phase and strength of the relationship between forest fires and most common boreal tree taxa in a time–frequency window. Pollen and stomata data show that all of the modern-day common tree taxa, including Norway spruce ( Picea abies) and Siberian larch, have been present in the study region since the early Holocene. The absence of charcoal layers at Mosquito Hollow suggests that this site has acted as a fire-free refugium with continuous dominance of spruce throughout the Holocene. Meanwhile, the Larix Hollow record indicates frequent local fire events and as a consequence, a more variable tree species composition. The wavelet coherence results show that the impact of forest fires on vegetation varies from short-term (<200-year periods) changes in individual tree taxa to long-term (400–800 years) changes in forest composition, such as the expansion of spruce population after local high-intensity fires around 7500–7000 cal. yr BP and the increase in abundance of birch and alder during periods of high fire frequency. Our results suggest that Holocene fire histories can be markedly different within a small geographical area, demonstrating the importance of site-specific factors in the local fire regime in the unmanaged taiga forest.

Determining range edges: habitat quality, climate or climate extremes?

AbstractAimClimate change is predicted to adversely affect wildlife populations at the trailing edge of their range, with extreme weather events acting as a catalyst for local extinctions and range contractions. We assessed the relative importance of long‐term climate averages, short‐term drought and habitat in predicting species occupancy and range edge, using the koala (Phascolarctos cinereus) as a case study.LocationQueensland, Australia.MethodsWe used mixed effects models to quantify the influence of habitat quality and climate on koala distribution at the trailing edge of their range, at three spatial scales. We used piecewise logistic regression to estimate thresholds in the relationship between the range edge and key environmental variables.ResultsBoth climatic and habitat variables explained koala presence. At the site scale, the quality of habitat was important within landscapes that had experienced higher levels of rainfall during a decade‐long drought. The spatial pattern of the koala's present‐day western range limit reflects closely a breakpoint of ~350 mm in summer rainfall during the drought years, supporting both theoretical predictions and empirical research on the influence of climate extremes on contracting edge populations.Main conclusionsThe distribution of fauna at their range margin in semi‐arid regions reflects extreme climate events, such as drought. Within suitable climate conditions, habitat quality is important in determining site occupancy. The identification and protection of habitat refugia, where local microclimates and habitat characteristics can mitigate the impacts of extreme events on fauna species at the contracting edge of the range, may allow species to persist for longer under changing climate conditions.

Revised distribution and phytosociological data of Orobanche coerulescens Stephan in Willd. (Orobanchaceae): Poland in relation to Central Europe

Abstract Orobanche coerulescens has a Eurasian distribution. The species is classified as extinct at most of its localities at the western limit of its range. Its populations are very scarce and critically endangered in Central Europe. This work presents the current distribution of O.coerulescens in Poland, based on a critical revision of herbarium and literature data as well as results of original field research, and reviews its distribution in Central Europe (partly in Eastern Europe). Habitats, plant communities, and migration routes of O.coerulescens in Central Europe are discussed. The species was initially known in Poland from now historical localities in Pomerania and the valley of the lower Vistula. In 2000-2011 it was recorded at 9 localities in Podlasie, the Małopolska Upland (Wyżyna Małopolska), and the Łódź Hills (Wzniesienia Łódzkie). Its abundance at the localities ranged from a few to over 1000 shoots. These are the largest populations of O.coerulescens at its western and north-western range limits.

The Holocene boreal forest dynamics in the western range limit of the Siberian Larch (Larix sibirica): evidence from stomata, pollen and charcoal records from small hollows

The development of research into the history of tree growth and inferred summer temperature changes in Yamalia spanning the last 2000 years is reviewed. One focus is the evolving production of tree-ring width (TRW) and tree-ring maximum-latewood density (MXD) larch (Larix sibirica) chronologies, incorporating different applications of Regional Curve Standardisation (RCS). Another focus is the comparison of independent data representing past tree growth in adjacent Yamalia areas: Yamal and Polar Urals, and the examination of the evidence for common growth behaviour at different timescales. The sample data we use are far more numerous and cover a longer time-span at Yamal compared to the Polar Urals, but Yamal has only TRW, while there are both TRW and MXD for the Polar Urals. We use more data (sub-fossil and from living trees) than in previous dendroclimatic studies in this region. We develop a new TRW chronology for Yamal, more than 2000 years long and running up to 2005. For the Polar Urals we develop new TRW and MXD chronologies that show good agreement at short (<15 years) and medium (15–100 years) timescales demonstrating the validity of attempts to reconcile the evidence of longer-timescale information that they provide. We use a “conservative” application of the RCS approach (two-curve signal-free RCS), guarding against the possibility of “modern sample bias”: a possible inflation of recent chronology values arising out of inadvertent selection of mostly relatively fast-growing trees in recent centuries. We also transform tree indices to have a normal distribution to remove the positive chronology skew often apparent in RCS TRW chronologies. This also reduces the apparent magnitude of 20th century tree-growth levels.There is generally good agreement between all chronologies as regards the major features of the decadal to centennial variability. Low tree-growth periods for which the inferred summer temperatures are approximately 2.5 °C below the 1961–90 reference are apparent in the 15-year smoothed reconstructions, centred around 1005, 1300, 1455, 1530, particularly the 1810s where the inferred cooling reaches −4 °C or even −6 °C for individual years, and the 1880s. These are superimposed on generally cool pre-20th century conditions: the long-term means of the pre-1900 reconstructed temperature anomalies range from −0.6 to −0.9 °C in our alternative reconstructions. There are numerous periods of one or two decades with relatively high growth (and inferred summer temperatures close to the 1961–1990 level) but at longer timescales only the 40-year period centred at 250 CE appears comparable with 20th century warmth. Although the central temperature estimate for this period is below that for the recent period, when we take into account the uncertainties we cannot be highly confident that recent warmth has exceeded the temperature of this earlier warm period. While there are clear warm decades either side of 1000 CE, neither TRW nor MXD data support the conclusion that temperatures were exceptionally high during medieval times. One previous version of the Polar Urals TRW chronology is shown here to be in error due to an injudicious application of RCS to non-homogeneous sample data, partly derived from root-collar samples that produce spuriously high chronology values in the 11th and 15th centuries. This biased chronology has been used in a number of recent studies aimed at reconstructing wider scale temperature histories. All of the chronologies we have produced here clearly show a generally high level of growth throughout their most recent 80 years. Allowing for chronology and reconstruction uncertainty, the mean of the last 100 years of the reconstruction is likely warmer than any century in the last 2000 years in this region.

259 Long-term boreal forest dynamics at the modern western range limit of the Siberian larch (Larix sibirica), new insights from stomata and pollen records

259 Long-term boreal forest dynamics at the modern western range limit of the Siberian larch (Larix sibirica), new insights from stomata and pollen records

Western Range Boundaries Of Floodplain Trees in the Southeastern United States

.Forest vegetation in the southeastern United States extends westward beyond the Ozark and Ouachita plateaus in Arkansas and Missouri into the Central Plains. Along this transect, luxuriant forests give way to mixed forests and grasslands that include smaller trees and progressively fewer tree species and eventually to grassland‐dominated landscapes in central Kansas, Oklahoma, and Texas. This transition is directly related to decreasing precipitation with distance to the west of the Mississippi River valley. Many species, however, have abrupt western range boundaries related to physiography and hydrogeomorphic processes. The western range limits for many trees correspond to Coastal Plain boundaries that at a regional scale impose sharper range boundaries than would be expected on the basis of decreasing precipitation. Also, riparian habitats within stream valleys extending westward from the Coastal Plain provide suitable habitats for trees in the dry regions of the Great Plains. The presence of riparian trees in this region is determined largely by the presence or absence of groundwater conditions necessary for survival. For floodplain trees, then, it is primarily habitat—not climate—that determines the location of range boundaries.

Population Differentiation of Impatiens capensis (Balsaminaceae) at the Range Limit

A plant species that occupies a large geographic range must survive in a variety of environments. Impatiens capensis, an herbaceous annual that grows contiguously from the east coast of North America to the Colorado Rocky Mountains, prefers moist environments and is easily susceptible to drought. Impatiens populations at the species’ western range limit (Colorado) must endure a dramatically different environment than eastern populations do (Rhode Island and Illinois). This study investigated the stress response of a weedy annual at its range limit by examining how regional populations of I. capensis morphologically, physiologically, and phenologically adjust to drought. The results suggest that each population has evolved along a different evolutionary axis; each population exhibits a unique strategy for responding to drought stress. Rhode Island populations have evolved along a temporal axis to avoid stress with an accelerated phenology. An Illinois population has evolved along a physiological axis and exhibits a drought-tolerance strategy. Colorado populations have evolved along a morphological axis and tolerate drought. Thus, dealing with drought stress may involve population differentiation along different axes of functional plasticity.

Nine-Banded Armadillo (Dasypus novemcinctus) Records in New Mexico, USA

New Mexico represents the western range limit of the nine-banded armadillo (Dasypus novemcinctus) in the United States, although the nearest known established populations are in adjacent western Texas (Layne, 2003). Early records of armadillos in New Mexico were based on incidental observations (Findley et al., 1975). Stuart and Knight (1998) provided a comprehensive synopsis of scattered literature records and additional new observations of the armadillo in New Mexico, although that publication is difficult to access. Most recently, Stuart et al. (2007) provided records of the first armadillo specimens collected and preserved in the state and a map of all known locality records of armadillos in New Mexico, but did not give details about previous records. They concluded that while many records were likely the result of human intervention, at least some from southeastern New Mexico were possibly of natural origin and that suitable habitat exists in this part of the state (Stuart et al., 2007). Herein we provide a complete synopsis of all records of Dasypus novemcinctus in New Mexico known to us, including localities, dates, and sources of information. A map of these locations (Figure 1) shows that records are from the eastern third of New Mexico, which delineates the northwestern range limits of the species as currently understood. Each record is provided as a direct quote of the locality data taken from the cited source. Additional data on a record are in brackets and the reference is in parentheses. Bold numbers in parentheses correspond to localities mapped in Figure 1 and in several cases refer to two or more records from the same locality or geographically similar locations. Abbreviations include: DOR = dead on road; MSB = Museum of Southwestern Biology, University of New Mexico.

Nest Ecology of the Southern Two-lined Salamander (Eurycea cirrigera) in Eastern Illinois

1,* Abstract - Peripherally distributed populations of animals often exhibit differ- ent life-history parameters compared to those from more central locations. We report on the ecology of Eurycea cirrigera (Southern Two-lined Salamander) from its western range limit in eastern Illinois. We searched two streams and an intervening ridge from April 2002 until December 2003 to monitor clutch size and seasonal abundance of life stages. Oviposition began in April, and larvae were de- tected by late May. Mean clutch size was smaller than estimates from other parts of the species' range and did not covary with snout-vent length of the attending female. Nest-attendance rates we detected tended to be lower than previous es- timates. As in other parts of their range, clutches were often found under rocks with at least one other clutch. Longer rocks were 1.30 times more likely to have multiple nests deposited under them.