Breeding biology of American crows in Saskatchewan parkland habitat

1991 ◽  
Vol 69 (1) ◽  
pp. 168-175 ◽  
Author(s):  
Jordan B. Ignatiuk ◽  
Robert G. Clark
Keyword(s):  
Hatching Success ◽  
Egg Laying ◽  
Breeding Biology ◽  
Breeding Habitat ◽  
Breeding Sites ◽  
Corvus Brachyrhynchos ◽  
Aspen Parkland ◽  
American Crows ◽  
Clutch Initiation ◽  
Bill Length

The breeding biology of American crows (Corvus brachyrhynchos) was studied in two areas (St. Denis and Elstow) of aspen parkland habitat in Saskatchewan, Canada, in 1987 and 1988. The St. Denis area had relatively more diverse land use and contained more wetlands than the Elstow area. Crows returned from winter ranges in early April and were frequently observed at breeding sites in late April, when nest building began. Overall, mean (± SD) clutch initiation dates were 6 May (± 6 days) at St. Denis and 10 May (± 6) at Elstow, but, in 1988, clutches were initiated about 6 days earlier at St. Denis than at Elstow (P < 0.05). Density of nests at St. Denis averaged twice that found at Elstow (0.70 and 0.35/km2, respectively; P < 0.05). Size of incubated clutches did not differ between years or areas, and averaged 4.8 ± 0.6 eggs (n = 104). Hatching success did not differ by year or area, but in 1987, nests at St. Denis produced nearly twice as many young as at Elstow. Brood losses resulted from predation, starvation, and possibly other factors. Chicks in smaller broods gained mass faster and fledged at a lighter mass than chicks in larger broods. There were no consistent differences between areas in the mass, bill length, and head–bill lengths of 22-day-old chicks. Young fledged when they were between 30 and 34 days old. Crows at St. Denis had higher reproductive success (1987), nested at greater densities (1988 and both years combined), and began egg laying earlier (1988) than at Elstow, suggesting that St. Denis was a more productive breeding habitat.

scholarly journals Nest success and conservation status of the Blue Swallow Hirundo atrocaerulea in Swaziland

2006 ◽  
Vol 16 (3) ◽  
pp. 187-196 ◽  
Author(s):  
ARA MONADJEM ◽  
RICHARD C. BOYCOTT ◽  
KIM ROQUES ◽  
RAY GAMA ◽  
DAVID GARCELON
Keyword(s):  
Total Population ◽  
Conservation Status ◽  
Significant Proportion ◽  
Egg Laying ◽  
Breeding Habitat ◽  
Sub Saharan Africa ◽  
Breeding Sites ◽  
Double Brooding ◽  
Sub Saharan ◽  
Timber Plantations

The Blue Swallow Hirundo atrocaerulea is a globally threatened species endemic to sub-Saharan Africa. The total population breeding south of the Limpopo River (i.e. in South Africa and Swaziland) probably numbers around 100 pairs. A significant proportion of these birds breed in Swaziland, but to date little has been published on this population. Suitable breeding habitat has been reduced significantly in the country in recent decades, due mostly to afforestation with exotic timber plantations, with urbanization playing a lesser role. In Swaziland, breeding sites are restricted to grasslands above 1,200 m, but mostly above 1,300 m. Timing of egg laying is bimodal indicating double brooding. The number of nests initiated in a season is weakly correlated with rainfall in preceding months. Nests were built predominantly in disused antbear Orycteropus afer burrows, with smaller numbers in natural sinkholes. Mean clutch size was 2.80, and 61% of eggs laid resulted in fledged offspring. Mean productivity was 1.30 fledglings per pair per nest attempt. These figures suggest that breeding success is not currently being reduced in Swaziland. The minimum total population currently thought to be breeding in Swaziland is 10 pairs, but this is based on intensive studies of only part of the suitable range. It is recommended that a complete survey be conducted covering the entire range of the species in Swaziland.

scholarly journals Drone assessment of habitat selection and breeding success of Gull-billed Tern Gelochelidon nilotica nesting on low-accessibility sites: a case study

2021 ◽  
Vol 90 (2) ◽  
Author(s):  
Francesco Scarton ◽  
Roberto Valle
Keyword(s):  
Habitat Selection ◽  
Breeding Success ◽  
Hatching Success ◽  
Ground Level ◽  
Breeding Biology ◽  
Nest Attendance ◽  
Fish Farms ◽  
Breeding Sites ◽  
Water Edge

The use of drones in the study of waterbird breeding biology has received considerable attention in the last years, but very few studies were made along the Mediterranean. We studied habitat selection and breeding success of the Gull-billed Tern Gelochelidon nilotica in two colonies inside fish farms along the Italian Adriatic coastline, using a small, commercial drone. Both colonies were located on small islets surrounded by very shallow water and clayey bottoms, thus being difficult to access. Compared with availability, the Gull-billed Terns selected quadrats higher above the water level, with a higher vegetation cover, which lay farther from the water edge, contain less water, and which are more frequently located in the center of the islands. 147 of 178 clutches (mean clutch size ± SD: 2.61 ± 0.58) hatched 383 chicks (82.5%; 2.15 ± 1.09 chicks per nest), with large differences between the two colonies. Hatching success was 95.0% and 69.1%; the most common cause of egg loss was flooding (97.0%). Nest attendance could easily be ascertained by 30-m above ground level drone-derived imagery. The use of a drone allowed the study of some aspects of the breeding biology of the Gull Billed Tern in two breeding sites where the traditional field approach, i.e. researchers reaching the sites by boat, would have been very difficult, causing unavoidable and prolonged disturbance to the nesting adults.

The breeding biology of two Lake Erie herring gull colonies

1977 ◽  
Vol 55 (5) ◽  
pp. 796-805 ◽  
Author(s):  
Ralph D. Morris ◽  
Gerard T. Haymes
Keyword(s):  
Reproductive Success ◽  
Clutch Size ◽  
Lake Erie ◽  
Hatching Success ◽  
Early Period ◽  
Breeding Biology ◽  
Nest Density ◽  
Herring Gull ◽  
Event Recorder ◽  
Clutch Initiation

The breeding biology of two Lake Erie herring gull colonies was studied from 1973 to 1976, emphasizing effects of clutch size and time of clutch initiation on reproductive success. In 1976, incubation attention of two-egg and three-egg clutches started early and late in the season was measured with a 20-pen event recorder. Chlorinated hydrocarbon residues in eggs were assessed in 2 years. Nest density was greater, clutch initiation more synchronized, and hatching success higher at one of the colonies. Hatching success and fledging success were independent of clutch size bin early nesters were more successful than late nesters. Differences in hatching success between two-egg and three-egg clutches were a function of time of clutch initiation such that the clutch size with the greater proportion of its nests in the early period had a higher hatching success. The reproductive success of the Lake Erie colonies was intermediate among rates reported for other Great Lakes colonies but below those of most eastern North American or European colonies. There were no significant differences in the incubation attention between two-egg clutches and three-egg clutches or between early and late three-egg clutches. Most clutches were incubated greater than 95% of the time although clutches incubated less than 75% realized the same hatching success.

Breeding biology of the Critically Endangered Tahiti MonarchPomarea nigra, a bird with a low productivity

2017 ◽  
Vol 28 (4) ◽  
pp. 606-619 ◽  
Author(s):  
CAROLINE BLANVILLAIN ◽  
THOMAS GHESTEMME ◽  
TEHANI WITHERS ◽  
MARK O’BRIEN
Keyword(s):  
Reproductive Success ◽  
French Polynesia ◽  
Egg Laying ◽  
Breeding Biology ◽  
Critically Endangered ◽  
Tropical Island ◽  
Island Endemics ◽  
Nest Activity ◽  
Considerable Length ◽  
One Year

SummaryWe studied the breeding biology of Tahiti MonarchPomarea nigra, a ‘Critically Endangered’ forest bird endemic to Tahiti (French Polynesia). Nest activity was monitored from 1998 to 2002, and again from 2008 to 2015. During these 12 years, only 2–13 breeding pairs per year produced hatchlings. Egg-laying occurred all year, but usually increased between August and January, peaking around November. Of the 200 nests monitored, 33 (16%) were abandoned shortly after construction, 71 had an egg laid immediately after the nest were completed (34 %) and 96 nests (46 %) had a pre-incubation phase of 18.9 ± 1.9 days (3–62 days;n= 47 nests), during which the birds visited the nest on an irregular basis. Half (49 of 96) of these nests were abandoned before an egg was laid, with incubation subsequently commencing at the remaining nests (n= 47). Although both sexes incubated for an average of 13.6 ± 0.3 days (range 13–15), the female usually spent more time incubating than the male. Only one young per nest was ever observed. The average nestling phase was 15.5 ± 0.7 days (range 13 to 20 days). Parents continue to feed the young after fledging for 74 ± 4.7 days (range 42–174). As with many tropical island endemics, the Tahiti Monarch has low reproductive productivity as indicated by the fact that: 1) only 56% of pairs attempt to lay an egg in any one year, 2) most pairs attempt only one brood per year and 3) the considerable length of the nesting and fledging phases. Because of its low productivity, maximising the reproductive success of the Tahiti Monarch is essential to secure its recovery.

scholarly journals Effects of constant incubation regimes on eggs and hatchlings of the egg-laying skink, Oligosoma suteri

2021 ◽  
Author(s):  
◽  
Kelly Maree Hare
Keyword(s):  
Hatching Success ◽  
Incubation Temperature ◽  
Unit Length ◽  
Condition Index ◽  
Egg Laying ◽  
Maternal Influence ◽  
Temperature Dependent ◽  
Sprint Speed ◽  
Fitness Traits ◽  
Incubation Temperatures

<p>The conditions under which reptilian eggs are incubated affect survival probability and physiological attributes of the progeny. The egg-laying skink, Oligosoma suteri, is the only endemic oviparous lizard in New Zealand. No controlled laboratory incubation had previously been undertaken, and thus no information was available on the requirements for successful captive incubation. I studied the effects of incubation regime on the eggs and hatchlings of O. suteri to four months of age. Oligosoma suteri eggs (n = 174) were randomly distributed among three constant incubation temperatures (18°C, 22°C and 26°C) and two water potentials (-120 kPa and -270 kPa). Hatching success and hatchling survival were greatest at 22°C and 26°C, with hatchlings from 18°C incubation suffering from physical abnormalities. Incubation regime and maternal influence did not affect sex of individuals, with equal sex ratios occurring from each incubation treatment. Hatchlings from the 22°C and -120 kPa incubation treatments were larger, for most measurements, and warmer incubation temperatures resulted in increased growth rates. Juveniles from 22°C and 26°C and individuals with greater mass per unit length (condition index) sprinted faster over 0.25 m. Sprint speed was positively correlated with ambient temperature. At four months of age sprint speed decreased in 18°C individuals and individuals incubated at 26°C and -270 kPa compared to their performance at one month. The results suggest that the most successful captive incubation regime for O. suteri is 22°C and -120 kPa. This study also shows that temperature-dependent sex determination does not occur in O. suteri, but that fitness traits are influenced by incubation temperature.</p>

scholarly journals Water-filled Asian elephant tracks serve as breeding sites for anurans in Myanmar

Mammalia ◽  
2019 ◽  
Vol 83 (3) ◽  
pp. 287-289
Author(s):  
Steven G. Platt ◽  
David P. Bickford ◽  
Myo Min Win ◽  
Thomas R. Rainwater
Keyword(s):  
Loxodonta Africana ◽  
Ecosystem Engineering ◽  
Asian Elephant ◽  
Breeding Habitat ◽  
Elephas Maximus ◽  
Stepping Stones ◽  
Breeding Sites ◽  
Loxodonta Cyclotis ◽  
And Function

Abstract Elephants are widely recognized as ecosystem engineers. To date, most research on ecosystem engineering by elephants has focused on Loxodonta africana and Loxodonta cyclotis, and the role of Elephas maximus is much less well-known. We here report observations of anuran eggs and larva in water-filled tracks (n=20) of E. maximus in Myanmar. Our observations suggest that water-filled tracks persist for >1 year and function as small lentic waterbodies that provide temporary, predator-free breeding habitat for anurans during the dry season when alternate sites are unavailable. Trackways could also function as “stepping stones” that connect anuran populations.

scholarly journals West Nile Virus Devastates an American Crow Population

The Condor ◽  
2005 ◽  
Vol 107 (1) ◽  
pp. 128-132 ◽  
Author(s):  
Carolee Caffrey ◽  
Shauna C. R. Smith ◽  
Tiffany J. Weston
Keyword(s):  
West Nile Virus ◽  
North America ◽  
Late Summer ◽  
Total Loss ◽  
West Nile ◽  
American Crow ◽  
Corvus Brachyrhynchos ◽  
American Crows

Abstract In its spread west across North America in 2002, West Nile virus (WNV) reached a population of marked American Crows (Corvus brachyrhynchos) in Stillwater, Oklahoma, in late summer. Within two months, 46 of 120 individuals were missing or known to be dead, 39 of which (33% of the population) are estimated to have died for WNV-related reasons. In 2003, 56 of 78 marked crows disappeared or were found dead between June and November. Five of the 28 juvenile losses were possibly unrelated to WNV, thus we estimate that 65% of our population died because of this pathogen in 2003. The total loss of 72% of population members, including 82% of juveniles, in a single year of WNV exposure raises concern for precipitous declines in American Crow populations in coming years. El Virus del Nilo Occidental Devasta una Población de Corvus brachyrhynchos Resumen. En su diseminación hacia el oeste de América del Norte durante 2002, el Virus del Nilo Occidental alcanzó a fines del verano una población marcada de Corvus brachyrhynchos en Stillwater, Oklahoma. En menos de dos meses, 46 de los 120 individuos registrados desaparecieron o murieron, 39 de los cuales (33% de la población) estimamos que murieron por causas relacionadas con el virus. En 2003, 56 de los 78 cuervos marcados desaparecieron o fueron encontrados muertos entre junio y noviembre. Cinco de las 28 pérdidas de juveniles posiblemente no estuvieron relacionadas con el virus, por lo que estimamos que el 65% de nuestra población murió a causa de este patógeno en 2003. La pérdida total del 72% de los miembros de la población, incluyendo el 82% de los juveniles, en un solo año de exposición al virus plantea preocupaciones en cuanto a la posibilidad de una disminución precipitada de las poblaciones de C. brachyrhynchos en los próximos años.

scholarly journals Breeding biology of coppersmith barbet, Megalaima haemacephala (Müller, 1776)

2013 ◽  
Vol 31 ◽  
pp. 31-34
Author(s):  
Noor Jahan Sarker ◽  
M Firoj Jaman ◽  
Shariar Mustafa ◽  
Md Saidur Rahman
Keyword(s):  
Incubation Period ◽  
Breeding Season ◽  
Breeding Success ◽  
Brood Size ◽  
Botanical Garden ◽  
Egg Laying ◽  
Breeding Biology ◽  
Average Weight ◽  
Average Height ◽  
Average Depth

Breeding biology of the Coppersmith barbet, Megalaima haemacephala (Müller, 1776) was carried out between February, 2006 and January, 2007 at Sharawardy Uddyan, Ramna Park, Curzon Hall and National Botanical Garden. The breeding season started from December and ended in June. In total 20 nests were observed, of which 10 nests were studied in details in four study areas. The coppersmith barbet mostly preferred to make holes on the branches of koroi (Albizzia procera) for nesting. Egg laying started on 15th February in the study areas. Average height of nests from the ground was 9.7m and average depth and diameter of the holes was 29.20cm and 4.46cm respectively. New holes were constructed yearly or the old one was reused. Both the sexes took part in incubation of eggs, brooding and feeding to the nestlings. A total of 30 eggs were laid in 10 nests. Clutch size varied from 2 – 4 eggs (average: 3 eggs). Among them, 20 (66.67%) eggs were hatched and the rest 10 (33.33%) were unhatched and lost. Average incubation period was 14 days. The male and the female incubated the eggs for an average of 27.44 minutes/ hours and 32.56 minutes/ hours, respectively. Average number of nestlings (brood size) per nest was 2. Out of 20 nestlings, 16 left their nests successively. The breeding success was 53.33% in relation to the number of eggs laid and 80% in relation to nestlings hatched. The average weight of eggs and nestlings was 3.59g and 9.33g, respectively. The main causes of loss of the eggs and nestlings were human interference, predation and ectoparasitic infections. Insects and fruits were fed to the nestlings by their parents.DOI: http://dx.doi.org/10.3329/ujzru.v31i0.15397Univ. j. zool. Rajshahi Univ. Vol. 31, 2012 pp. 31-34 

scholarly journals The Inflected Alarm Caw of the American Crow: Differences in Acoustic Structure Among Individuals and Sexes

The Condor ◽  
2006 ◽  
Vol 108 (3) ◽  
pp. 518-529 ◽  
Author(s):  
Jessica L. Yorzinski ◽  
Sandra L. Vehrencamp ◽  
Kevin J. McGowan ◽  
Anne B. Clark
Keyword(s):  
Individual Differences ◽  
Function Analysis ◽  
Acoustic Measurements ◽  
American Crow ◽  
Acoustic Structure ◽  
Corvus Brachyrhynchos ◽  
Call Structure ◽  
American Crows ◽  
The Status ◽  
Family Membership

Abstract Previous research on individual differences in the acoustic structure of vocalizations and vocal recognition has largely focused on the contexts of parent-offspring interactions, territory defense, sexual interactions, and group cohesion. In contrast, few studies have examined individual differences in the acoustic structure of mobbing and alarm calls. The purpose of this study was to explore individual differences in the acoustic structure of the inflected alarm caw of the American Crow (Corvus brachyrhynchos). The alarm caws of 15 wild, marked individuals were recorded and 25 acoustic measurements were made automatically using customized software. A stepwise discriminant function analysis showed that 20 of the 25 variables were important in discriminating among individuals, with 65% classification success. We used factor analysis to reduce the large number of variables to a set of seven meaningful call features. All of these features differed among individuals, suggesting that American Crows have the potential to discriminate among individual birds on the basis of call structure alone. Five of the features differed between the sexes, with call frequency being the most significant. One clearly subordinate male clustered with the females, raising the possibility that social status partially determines the sex-based differences. Encoding of individual identity in alarm contexts may be adaptive if receiver vigilance and approach urgency depend on the status, reliability, or family membership of the alarm signaler.

scholarly journals In-situ severe breeding habitat intervention only achieves temporary success in reducing Batrachochytrium dendrobatidis infection

2020 ◽  
Vol 41 (2) ◽  
pp. 261-267 ◽  
Author(s):  
Andrés Fernández-Loras ◽  
Luz Boyero ◽  
Jaime Bosch
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Research Effort ◽  
Breeding Habitat ◽  
Habitat Manipulation ◽  
Breeding Sites ◽  
Breeding Habitats ◽  
The Common ◽  
Natural Breeding ◽  
Midwife Toad

Abstract Chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd), is causing sharp declines in amphibian populations around the globe. A substantial research effort has been made to study the disease, including treatments against Bd, but most treatments have been applied to captive amphibians only. We report a study aimed at clearing wild populations of the Common Midwife toad Alytes obstetricans. We removed all larvae from natural breeding sites (cattle troughs) and conducted two types of severe breeding habitat manipulation (complete drying and fencing for the whole breeding season). While larval removal followed by drying was a successful method of Bd elimination, the effect was only temporary. Since terrestrial habits of adult A. obstetricans prevent them from infection, our findings suggest that, even in simple breeding habitats where all aquatic amphibian stages can be handled and extreme habitat intervention is possible, Bd cannot be eliminated without controlling other potential Bd reservoirs in the surroundings of breeding sites.

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