scholarly journals Colony Development and Density-Dependent Processes in Breeding Grey Herons

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Takeshi Shirai
Keyword(s):  
Colony Size ◽  
Single Species ◽  
Colony Development ◽  
First Year ◽  
Saturation Curve ◽  
Density Dependent ◽  
Ardea Cinerea ◽  
Prolonged Duration ◽  
Nestling Feeding ◽  
Dependent Processes

The density-dependent processes that limit the colony size of colonially breeding birds such as herons and egrets remain unclear, because it is difficult to monitor colonies from the first year of their establishment, and the most previous studies have considered mixed-species colonies. In the present study, single-species colonies of the Grey Heron (Ardea cinerea) were observed from the first year of their establishment for 16 years in suburban Tokyo. Colony size increased after establishment, illustrating a saturation curve. The breeding duration (days from nest building to fledging by a pair) increased, but the number of fledglings per nest decreased, with colony size. The reproductive season in each year began earlier, and there was greater variation in the timing of individual breeding when the colony size was larger. The prolonged duration until nestling feeding by early breeders of the colony suggests that herons at the beginning of the new breeding season exist in an unsteady state with one another, likely owing to interactions with immigrant individuals. Such density-dependent interference may affect reproductive success and limit the colony size of Grey Herons.

scholarly journals First year of the new Arctic AWIPEV-COSYNA cabled Underwater Observatory in Kongsfjorden, Spitsbergen

2016 ◽  
Author(s):  
Philipp Fischer ◽  
Max Schwanitz ◽  
Reiner Loth ◽  
Uwe Posner ◽  
Markus Brand ◽  
...  
Keyword(s):  
Statistical Power ◽  
Single Species ◽  
First Year ◽  
Total Abundance ◽  
Digital Sampling ◽  
Scientific Analysis ◽  
Data Density ◽  
Species Abundances ◽  
Sampling Procedures ◽  
Total Species

Abstract. A combined year round assessment of selected oceanographic data and a macrobiotic community assessment was performed from October 2013 to November 2014 in the littoral zone of the polar fjord systems Kongsfjorden on the west coast of Svalbard (Norway). A state of the art remote controlled cabled underwater observatory technology was used for daily vertical profiles of temperature, salinity and turbidity together with a stereo-optical assessment of the macrobiotic community, including fish. The results reveal a distinct seasonal cycle in total species abundances with a significantly higher total abundance and species richness during the polar winter when no light is available under water compared to the summer months when 24-h light is available. During the winter months, a temporally highly segmented community was observed with respect to species occurrence with single species dominating the winter community for restricted times. In contrast, the summer community showed an overall lower total abundance, as well as a significantly lower number of species. The study clearly demonstrates the high potential of cable connected remote controlled digital sampling devices, especially in remote areas, such as the polar fjord systems, with harsh environmental conditions and limited accessibility. A smart combination of such new digital “sampling” methods with classic sampling procedures can provide a possibility to significantly extend the sampling time and frequency especially in remote and difficult to access areas. This can help to provide a sufficient data density and therefore statistical power for a sound scientific analysis without increasing the invasive sampling pressure in ecologically sensitive environments.

scholarly journals PRODUCTIVITY OF PERENNIAL GRASSES AND MIXTURES WITH DIFFERENT SOWING DATES IN WESTERN SIBERIA

2020 ◽  
pp. 24-32
Author(s):  
V. A. Petruk
Keyword(s):  
Dry Matter ◽  
Crop Yields ◽  
Growing Season ◽  
Single Species ◽  
Field Studies ◽  
Perennial Grasses ◽  
First Year ◽  
Sowing Dates ◽  
Second Year ◽  
Sowing Period

The results of field studies for 2017 - 2019 are presented. yields of perennial grasses sown at different times of the growing season. Spring, summer, and winter sowing periods were compared. Alfalfa, clover, rump, and also their mixtures were sown in 2017 under the cover of barley. The value of the cover crop yield of spring and summer sowing periods did not differ significantly and amounted to 4-5 t / ha of absolutely dry matter. Winter barley crops have not formed. On average, over 2 years of use, the highest yields were observed in alfalfa-crust grass mixtures - 3.4 t / ha of absolutely dry matter. The lowest yield was obtained in the single-species seeding of the rump. Correspondingly, in the spring, summer and winter periods of sowing, the yield of rump was 1.6; 1.1 and 1.3 t / ha. With a late sowing period, the yield of perennial grasses is significantly lower compared to spring and summer. With winter sowing periods, the yield was the highest for grass stands of alfalfa and alfalfacrust grass mixture - 2.3 and 2.4 t / ha. It should be noted that in the second year of use, the yield by the sowing dates in single-species crops and grass mixtures is leveled. The winter crops of perennial grasses in the first year of use formed a low yield. Only in the second year (third year of life) the productivity of perennial grasses of winter sowing began to increase. Consequently, in the area under perennial grasses of the winter sowing period, during one growing season (the next year after sowing), the crop was not actually formed. Based on the data obtained, production can be recommended for spring and summer planting of perennial grasses under the cover of barley. The winter sowing period provides economically valuable crop yields only by the third year of life.

Multiple density-dependent processes shape the dynamics of a spatially structured amphibian population

2018 ◽  
Vol 88 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Hugo Cayuela ◽  
Benedikt R. Schmidt ◽  
Avril Weinbach ◽  
Aurélien Besnard ◽  
Pierre Joly
Keyword(s):  
Amphibian Population ◽  
Density Dependent ◽  
Dependent Processes

scholarly journals Large-Scale Variation in Growth of Black Brant Goslings Related to Food Availability

The Auk ◽  
2001 ◽  
Vol 118 (4) ◽  
pp. 1088-1095 ◽  
Author(s):  
James S. Sedinger ◽  
Mark P. Herzog ◽  
Brian T. Person ◽  
Morgan T. Kirk ◽  
Tim Obritchkewitch ◽  
...  
Keyword(s):  
Large Scale ◽  
Grazing Pressure ◽  
The Arctic ◽  
First Year ◽  
Principal Mechanism ◽  
Density Dependent ◽  
Brood Rearing ◽  
Branta Bernicla ◽  
Black Brant ◽  
Arctic Coast

AbstractWe examined variation in growth of Black Brant (Branta bernicla nigricans) goslings among two colonies on the Yukon-Kuskokwim Delta in southwestern Alaska and the Colville River Delta on Alaska's Arctic coast. We simultaneously measured abundance and quality of a key food plant, Carex subspathacea, and grazing pressure on that plant at the three colonies. Our goal was to measure variation in gosling growth in relation to variation in grazing pressure and food abundance because growth of goslings is directly linked to first-year survival, and consequently is the principal mechanism for density-dependent population regulation. Goslings grew substantially faster on the arctic coast and were nearly 30% larger than those on the Yukon-Kuskokwim Delta at four to five weeks old. Faster growth on the arctic coast was associated with 2× greater standing crop of C. subspathacea during brood rearing than on the Yukon-Kuskokwim Delta. Dispersal rates are high enough (Lindberg et al. 1998) to rule out local adaptation and genetic variation as explanations for observed variation in growth. Our results are consistent with lower survival of goslings from the Yukon-Kuskokwim Delta during their first fall migration and stronger density-dependent regulation on the Yukon-Kuskokwim Delta than on the Arctic coast.

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