scholarly journals Reproduction, Prey, and Habitat of the Aplomado Falcon (Falco Femoralis) in Desert Grasslands of Chihuahua, Mexico

The Auk ◽  
2004 ◽  
Vol 121 (4) ◽  
pp. 1081-1093 ◽  
Author(s):  
Alberto Macías-Duarte ◽  
Angel B. Montoya ◽  
W. Grainger Hunt ◽  
Alberto Lafón-Terrazas ◽  
Robert Tafanelli
Keyword(s):  
Nest Site ◽  
Plant Density ◽  
Breeding Population ◽  
Prey Abundance ◽  
Severe Drought ◽  
Bird Abundance ◽  
Start Date ◽  
Important Prey ◽  
Occupied Territory ◽  
Summer Rain

Abstract A breeding population of Aplomado Falcons (Falco femoralis) remains in the desert grasslands of Chihuahua, Mexico, despite their extirpation in the nearby southwestern United States. We monitored falcon reproduction at 35 territories during 1996-2002, a period of severe drought in the region. To test the influence of prey abundance and vegetation on falcon reproduction, we surveyed avian prey abundance through plot counts in 1998-2002 and characterized vegetation at each plot. Aplomado Falcon productivity declined from 1.57 fledglings per occupied territory in 1997 to 0.63 in 2002 at the larger of two study areas, a trend consistent with cumulative effects of consecutive years of low rainfall. Reproduction in the smaller area remained low throughout the study. Both productivity and incubation start date were significantly associated with prey bird abundance. Summer rain most likely influenced falcon reproduction by affecting seed abundance and therefore abundance of granivorous prey birds the following winter and spring. Falcons nested in open grasslands with sparse woody vegetation, an adaptation likely related to higher prey vulnerability and fewer predators. However, important prey birds were positively correlated with woody-plant density, which suggests that proximity of shrublands increased nest-site suitability.

Earliness of an indeterminate crop, Vigna unguiculata (L.) Walp., as affected by drought, temperature, and plant density

1982 ◽  
Vol 33 (3) ◽  
pp. 531 ◽  
Author(s):  
DA Grantz ◽  
AE Hall
Keyword(s):  
Vigna Unguiculata ◽  
Dry Matter ◽  
Plant Density ◽  
Severe Drought ◽  
Base Temperature ◽  
Semiarid Environments ◽  
Land Race ◽  
Sowing Dates ◽  
Moderate Drought ◽  
Extreme Variability

Earliness of an indeterminate crop, Vigna unguiculata (L.) Walp., was studied to aid development of selection techniques for improving adaptation to semiarid environments. Earliness was based upon the time of first appearance of floral buds and flowers, proportion of shoot dry matter in reproductive parts at midseason, and time of maturity. A cowpea land race, Chino 3, was earlier than cultivars California Blackeye No. 3 and No. 5, with respect to all of these criteria. Time to flowering from different sowing dates was related to heat units, which were calculated from daily mean air temperature above a base temperature of c. 10�C. The proportions of shoot dry matter in reproductive parts during early stages of pod-filling were greater with moderate drought but were unaffected by severe drought, compared with the response of adequately irrigated plants. Widely spaced plants exhibited greater proportions of shoot dry matter in reproductive parts at midseason than did closely spaced plants. Adaptation of cowpeas to semiarid environments may be improved by selecting for early partitioning of carbohydrates to reproductive parts. Selection for early partitioning may be more effective in adequately watered conditions, owing to extreme variability under drought, and at wide and precise spacing.

Nesting activity and demography of an isolated population of malleefowl (Leipoa ocellata)

2003 ◽  
Vol 30 (5) ◽  
pp. 451 ◽  
Author(s):  
David Priddel ◽  
Robert Wheeler
Keyword(s):  
Site Fidelity ◽  
Nest Site ◽  
Large Population ◽  
Breeding Population ◽  
Adult Mortality ◽  
High Rate ◽  
Nest Site Fidelity ◽  
Pair Bonds ◽  
South Wales ◽  
Nesting Activity

Nesting activity of a population of malleefowl (Leipoa ocellata), isolated within a small mallee remnant in central New South Wales, was monitored annually between the summers of 1986–87 and 1998–99. A total of 148 nesting events was recorded. Only once was a new mound constructed rather than an old one reworked. Birds began and finished work on the mound progressively later each month (October to January). Nest-site fidelity was highly variable; some pairs persisted with the same mound for up to nine years while others relocated between a cluster of two, three or four mounds. Males displayed greater nest-site fidelity than females. After the loss of a partner, males tended to continue to use mounds they had used previously whereas females often relocated to a new mound. All individuals were monogamous. Pair bonds were maintained for life but, following the death of a partner, new bonds were quickly established with another unattached individual. Established pairs occasionally failed to breed, all such failures being coincident with years of low rainfall. Pairs that did not breed generally began construction of a nest but failed to complete the task. As far as can be ascertained, unpaired birds did not construct nests. The malleefowl population was characterised by a rapid turnover of breeding individuals, a high rate of adult mortality and a lesser rate of recruitment. The maximum longevity recorded for breeding adults was 12 years; average longevity was 7.5 years. Twenty-five adults were lost from the breeding population over a period of 9 years; meanwhile, 14 birds entered the breeding population. Thus, the ratio of adult mortality to recruitment was 1.79 : 1.00. Between 1986–87 and 1997–98 the population declined from at least 32 breeding adults to 14, at an average exponential rate of decrease of 0.075. Large population decreases were coincident with years of low rainfall. This population of malleefowl is predicted to become extinct by 2008.

scholarly journals Numbers, distribution and nest site characteristics of Jackdaw Corvus monedula in Slovenia and its conservation status

Acrocephalus ◽  
2016 ◽  
Vol 37 (170-171) ◽  
pp. 123-150
Author(s):  
Luka Božič
Keyword(s):  
Large Scale ◽  
Agricultural Landscape ◽  
Nest Site ◽  
Population Distribution ◽  
Residential Buildings ◽  
Conservation Status ◽  
Breeding Population ◽  
Nest Site Selection ◽  
Mountainous Area ◽  
Corvus Monedula

Abstract In 2008, a coordinated census of Jackdaw Corvus monedula was carried out to assess breeding population, distribution and nest site selection in Slovenia. Data collection continued for unsurveyed areas in the 2009-2011 period, including information on former colonies and threats. A total of 663-794 Jackdaw pairs were recorded at 86 sites, while total Slovene breeding population was estimated to be in the range of 700-900 pairs. Over one third of pairs were recorded in Central Slovenia, notably the largest city Ljubljana (20.8%), followed by almost a quarter in the Podravje region. Most colonies numbered between 2 and 5 pairs, the largest occupying the Bežigrad district of Ljubljana (82-87 pairs). Large-scale density in geographically more or less uniform areas ranged from 3.65 pairs/10 km2 in the Sava plain to 0.15 pairs/10 km2 in mostly mountainous area in northern Slovenia. The majority of Jackdaws selected buildings for nesting (82.2% of pairs), while nesting in trees occurred less frequently (14.7%) and was almost entirely confined to the two easternmost regions of Slovenia. Nesting in cliffs was recorded at just two sites in Slovene Istria (3.1%). Average colony size differed significantly in relation to nest site type, with colonies in rock walls being on average the largest (median = 9.5 pairs), followed by colonies on buildings (6) and those in trees the smallest (3). Among pairs nesting on buildings, multi-storey residential buildings predominated (34.2%). A substantial percentage of population nested also on churches and tower blocks (14.4% and 13.5%, respectively). The highest percentage of pairs utilised holes in roofs (26.9%), followed by eaves (18.0%) and chimney pots (14.7%). Tree-nesting pairs occupied mostly small woods situated in open agricultural landscape. The most commonly used tree species was Beech Fagus sylvatica (53.1% of pairs) which hosted 14 of the total 16 forest colonies. For Jackdaws nesting in urban parks and avenues, plane trees Platanus sp. were the most important (30.6% of pairs). Their population stronghold was in lowlands, with 88.1% of pairs recorded at elevations under 400 m and the highest living colony in Slovenia at 578 m a.s.l. Jackdaws occurred on at least 54 specific sites in the past but became extinct there or declined severely by the time of this study. A minimum of 217-254 pairs were estimated lost at these sites, constituting a decline of 24% in c. 10-20 years. According to the IUCN criteria, Jackdaw would qualify as Vulnerable (VU) on the Red List of Slovenia. The commonest known cause of extinction/decline is renovation of buildings, a threat that is projected to escalate in the near future.

scholarly journals Breeding population decline and associations with nest site use of Leach’s Storm-Petrels on Kent Island, New Brunswick from 2001 to 2018

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Kyle J. N. d'Entremont ◽  
Laura Minich Zitske ◽  
Alison J. Gladwell ◽  
Nathan K. Elliott ◽  
Robert A. Mauck ◽  
...  
Keyword(s):  
New Brunswick ◽  
Nest Site ◽  
Population Decline ◽  
Breeding Population ◽  
Site Use

Diet and reproductive success of an Arctic generalist predator: Interplay between variations in prey abundance, nest site location, and intraguild predation

The Auk ◽  
2015 ◽  
Vol 132 (3) ◽  
pp. 735-747 ◽  
Author(s):  
Gilles Gauthier ◽  
Pierre Legagneux ◽  
Marc-André Valiquette ◽  
Marie-Christine Cadieux ◽  
Jean-François Therrien
Keyword(s):  
Reproductive Success ◽  
Intraguild Predation ◽  
Nest Site ◽  
Prey Abundance ◽  
Generalist Predator ◽  
Site Location

Drought legacy effects on post-fire vegetation dynamics in a Mediterranean shrubland of Central Spain

2020 ◽  
Author(s):  
Antonio Parra ◽  
María Belén Hinojosa ◽  
Iván Torres ◽  
José Manuel Moreno
Keyword(s):  
Plant Density ◽  
Rainfall Regime ◽  
Severe Drought ◽  
Summer Drought ◽  
Central Spain ◽  
Fire Cycle ◽  
Natural Rainfall ◽  
Legacy Effect ◽  
Mediterranean Shrubland ◽  
Rainfall Reduction

<p>Post-fire regeneration often occurs under water scarcity conditions in Mediterranean ecosystems. This fact is likely to be more frequent in the future, as climate change projections for the Mediterranean show increased temperature and decreased rainfall, as well as higher fire weather danger. Therefore, studying how vegetation responds to fire and drought is critical for anticipating vegetation vulnerability to global warming. Here, we present the results of a manipulative field study in a Mediterranean shrubland of Central Spain in which 4 drought treatments were imposed before and after carrying out an experimental burning of the treated plots: natural rainfall, historical rainfall regime (2 months summer drought per year), moderate drought (ca. 25% rainfall reduction from historical records, 5 months drought), and severe drought (ca. 50% rainfall reduction, 7 months drought). We monitored the plant community during the first 4 years after fire under the drought treatments followed by additional 6 years once such treatments had ceased. We found that drought significantly reduced density, cover, and size of seeder species during the first post-fire years under treatment. In contrast, resprouter species were virtually unaffected. As a whole, the changes in woody species dynamics resulted in a community ‘herbalization’, which was richer and more diverse, but probably more prone to a new fire. Moreover, we found that the drought effects on the community, and especially on the seeders, were maintained various years after all plots started receiving natural rainfall. 10 years after the fire, the legacy effect of the drought had been diluted, although some effects on plant density or cover in certain seeder species were still present. Overall, this means that what happens during the first few years after fire is extremely important for vegetation recovery, and that the effects of a long drought can persist over various years, and likely over a whole fire cycle.</p>

Comparison of winter-active phalaris with the Australian cultivar under rotational grazing. 1. Basal area and plant density

1996 ◽  
Vol 36 (3) ◽  
pp. 277 ◽  
Author(s):  
RA Culvenor ◽  
RN Oram
Keyword(s):  
Soil Fertility ◽  
Growth Rates ◽  
Plant Density ◽  
Basal Area ◽  
Breeding Population ◽  
Rotational Grazing ◽  
Deep Soil ◽  
Small Areas ◽  
Phalaris Aquatica ◽  
Significant Mortality

Basal area and plant density in fixed quadrats are presented from a grazing trial comparing the persistence of 2 'winter-active' cultivars (Sirosa, Holdfast) and a breeding population (Perla Retainer) of phalaris (Phalaris aquatica L.) possessing high seedling and winter growth rates with the original cultivar Australian. Four replicate pastures, 2 at each of 2 sites near Canberra, were grazed year-round at 15 wethers/ha for 3 years using a rotational system of management (2 weeks on, 4 weeks off,). The first site, The Elms, was located on a slope with shallow, coarse-textured soil; the second, Boundary Creek, was level with deep soil which was very acid in the upper 20 cm. Both sites were fertilised with superphosphate and, except for small areas, were limed before sowing. Significant mortality was observed only at The Elms during the summer-autumn drought after grazing commenced, when plant death was highest for Australian and lowest for Perla Retainer, an erect, summer-dormant population. Basal area of Australian and Sirosa, but not Holdfast and Perla Retainer, subsequently recovered. Australian established and maintained a 50-70% higher basal area due to a 30-40% higher area per plant and 15-25% more plants. The cultivars did not differ markedly in persistence measured as stability of basal area. However, Perla Retainer showed less vegetative expansion at the first site after grazing commenced and was considered less persistent than the cultivars there. Persistence was correlated with the productivity of individual plots, all cultivars being affected similarly. Regressions which varied with cultivar were derived in which basal area at establishment, but not subsequent changes in basal area under grazing, was positively related to soil fertility factors, mainly phosphorus, potassium and manganese. An association between the initial basal area of Sirosa and soil magnesium levels was also detected at 1 site. It was concluded from this study, which was conducted in the absence of major drought, that the winter-active cultivars of phalaris can be as persistent as Australian under rotational grazing and with adequate soil fertility, but that interactions with site will occur.

Harem size, territory quality, and reproductive success in the redwinged blackbird (Agelaius phoeniceus)

1977 ◽  
Vol 55 (8) ◽  
pp. 1261-1267 ◽  
Author(s):  
Patrick J. Weatherhead ◽  
Raleigh J. Robertson
Keyword(s):  
Reproductive Success ◽  
Nest Site ◽  
Selective Advantage ◽  
Breeding Population ◽  
Territory Size ◽  
Agelaius Phoeniceus ◽  
Breeding Density ◽  
Territory Quality ◽  
Fledging Success ◽  
Harem Size

The relationships between harem size, territory size, nest site suitability, and fledging success were studied for a breeding population of redwinged blackbirds (Agelaius phoeniceus). Reproductive success was correlated negatively with female breeding density within territories and positively with territory quality as determined from nest site parameters. Harem size was not correlated with differences in either territory area or quality. From these results we suggest that some females were attracted to nest in territories in which their chances of successful reproduction were lower than if they had chosen other available territories. To explain the selective advantage of such choices, we postulate that females were choosing mates which would enhance their ultimate fitness rather than their immediate reproductive success.

Feeding ecology of little tunny Euthynnus alletteratus in the central Mediterranean Sea

2007 ◽  
Vol 87 (4) ◽  
pp. 999-1005 ◽  
Author(s):  
Manuela Falautano ◽  
Luca Castriota ◽  
Maria Grazia Finoia ◽  
Franco Andaloro
Keyword(s):  
Mediterranean Sea ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Prey Abundance ◽  
Central Mediterranean ◽  
Size Classes ◽  
Larval Stages ◽  
Important Prey ◽  
Predator Size ◽  
Central Mediterranean Sea

The feeding habits of Euthynnus alletteratus and its variations compared to predator size in the central Mediterranean Sea were investigated. The stomach contents of 187 specimens were analysed, ranging from 26.8 to 50.3 cm total length, caught by authorized experimental drift-nets. The difference in food items found in the stomachs was evaluated by occurrence of prey frequency, prey weight, and prey abundance; these criteria were used to calculate an index of relative importance. Fish were the dominant food detected according to all numerical indicators examined and were mainly represented by Maurolicus muelleri and larval stages of teleosts. Hyperiid amphipods, dominated by Anchylomera blossevillei and Phrosina semilunata, were well represented in terms of frequency of occurrence. Variations in the diet composition compared to fish size were observed. Comparative analysis performed on prey abundance highlighted a trend of increasing predator size-classes among prey items. The specimens of the smallest sizes ate mainly adult clupeiforms and larvae or other juvenile teleosts. As fish grew, there were increased amounts of adult teleosts, crustaceans (hyperiids and isopods) and cephalopods. Maurolicus muelleri was the most important prey for the largest specimens analysed. Significant differences among size-classes, both in prey abundance and in prey weight, were confirmed by non-parametric multivariate analysis of variance (NP-MANOVA).

scholarly journals Nest-site preference of Griffon Vulture (Gyps fulvus) in Herzegovina

2012 ◽  
Vol 64 (1) ◽  
pp. 385-392 ◽  
Author(s):  
S.P. Marinkovic ◽  
Ljiljana Orlandic ◽  
S.B. Skoric ◽  
B.D. Karadzic
Keyword(s):  
Nest Site ◽  
Abundant Species ◽  
Breeding Population ◽  
Site Preference ◽  
Griffon Vulture ◽  
Gyps Fulvus ◽  
Dramatic Decline ◽  
Breeding Habitats ◽  
Using Data

Although formerly an abundant species, the Eurasian Griffon (Gyps fulvus Hablizl, 1783) has undergone a dramatic decline in Herzegovina. Such an unfavorable trend may be associated with frequent poisoning incidents (consumption of poisoned baits), shortage of food and hunting. This species disappeared from its breeding habitats in Herzegovina during the last decade of the 20th century. The extinction was probably caused by military activities during the civil war. Using data that were collected over a period of long-term (1980-1991) monitoring of the breeding population, we discovered optimal environmental conditions for the nesting of the Eurasian Griffon Vulture in Herzegovina. Information on nest-site preference is valuable for conservation programs and the possible reintroduction of the Eurasian Griffon, not only in Herzegovina, but also to a much wider region. During the study period, we observed 61 nests and 252 nesting cases in four colonies of Eurasian Griffon Vulture. Most nests were located on limestone and dolomite rocks. The average altitude of nests was 378 m a.s.l.; most of nests (85%) were located below 500 m a.s.l. Also, the majority of nests were located on west-exposed sites.

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