Optimal niche space of the redwinged blackbird (Agelaius phoeniceus). I. Nesting success in marsh and upland habitat

1972 ◽  
Vol 50 (2) ◽  
pp. 247-263 ◽  
Author(s):  
Raleigh J. Robertson
Keyword(s):  
Nesting Success ◽  
Predation Pressure ◽  
Agelaius Phoeniceus ◽  
Breeding Density ◽  
Niche Space ◽  
Fundamental Niche ◽  
Nesting Density ◽  
Different Parts

Survival value of different parts of the fundamental niche of the redwinged blackbird was determined by comparing nesting success in marsh and upland habitats. Marsh nesting populations had greater success than those in uplands because of a smaller proportion of nests destroyed by predators. Predation pressure in marshes was negatively correlated with the depth of water beneath the nest, and the synchrony and density of nesting in marshes in some cases has a swamping effect on local predator populations. The structure and phenology of marsh compared with upland vegetation is an important factor in determining nesting density and synchrony.Growth rates of nestlings and weight at fledging are similar between habitats. Genetic separation between marsh and upland populations is unlikely. Territoriality probably results in a limitation to breeding density in both habitats.The results support the hypothesis that where sympatric, redwings are excluded from their optimal niche space by yellow-headed blackbirds.

Reproductive responses of northern orioles to a changing food supply

1980 ◽  
Vol 58 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Spencer G. Sealy
Keyword(s):  
Food Supply ◽  
Malacosoma Disstria ◽  
Forest Tent Caterpillar ◽  
Breeding Density ◽  
Life Stages ◽  
Beach Ridge ◽  
Body Weights ◽  
Nesting Density ◽  
Late Instar ◽  
Tent Caterpillar

The response of the northern oriole (Icterus galbula) to an outbreak of the forest tent caterpillar (Malacosoma disstria) on the Delta Beach Ridge, Manitoba, was studied. Orioles responded in 1976 to the increased food supply by feeding on all life stages of the insect and by feeding late instar larvae and pupae to their young. The nesting density doubled in 1977, the 2nd year of the 2-year outbreak, but the caterpillar larvae died off before the orioles' chick-rearing period. The 1978 breeding density was back down to the level of 1976. Clutch sizes and body weights did not change despite the increase and eventual reduction in both food abundance and nesting density. Productivity was lower, and hatching failure and nestling death were higher, at the higher nesting density.

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.

Diel variation in signalling and signal transmission in the bladder grasshopper, Bullacris unicolor (Orthoptera; Pneumoridae)

Behaviour ◽  
2015 ◽  
Vol 152 (12-13) ◽  
pp. 1701-1718 ◽  
Author(s):  
Vanessa C.K. Couldridge ◽  
Mikhaila L. Gordon
Keyword(s):  
Intraspecific Variation ◽  
Signal Transmission ◽  
Signal Propagation ◽  
Transmission Conditions ◽  
Predation Pressure ◽  
Signal Timing ◽  
Diel Variation ◽  
Partial Support ◽  
Signal Attenuation ◽  
Different Parts

Here we investigate intraspecific variation in diel patterns of acoustic signalling in the bladder grasshopper, Bullacris unicolor. We observed that B. unicolor calls at different times during the night in different parts of its distribution. Males further north typically call just before dawn, while those further south signal throughout the night. Sound transmission experiments were conducted in order to determine whether the observed discrepancy in signal timing can be explained by differences in signal propagation at different times in the night, which might vary geographically. We found significant differences in signal attenuation and fidelity at different broadcast times as well as between locations. However, there was only partial support for the hypothesis that males time their calls to coincide with the most ideal transmission conditions. We suggest that other factors, such as predation pressure, might also contribute to the observed discrepancy in signal timing between populations.

Track 2.b Introduction: Design & Democracy

2019 ◽  
Vol 2 (1) ◽  
pp. 213
Author(s):  
Virginia TASSINARI ◽  
Ezio MANZINI ◽  
Maurizio TELI ◽  
Liesbeth HUYBRECHTS
Keyword(s):  
At Risk ◽  
Design Research ◽  
Core Theme ◽  
The Past ◽  
Noam Chomsky ◽  
Local Contexts ◽  
Democratic Discourse ◽  
Different Parts

The issue of design and democracy is an urgent and rather controversial one. Democracy has always been a core theme in design research, but in the past years it has shifted in meaning. The current discourse in design research that has been working in a participatory way on common issues in given local contexts, has developed an enhanced focus on rethinking democracy. This is the topic of some recent design conferences, such PDC2018, Nordes2017 and DRS2018, and of the DESIS Philosophy Talk #6 “Regenerating Democracy?” (www.desis-philosophytalks.org), from which this track originates. To reflect on the role and responsibility of designers in a time where democracy in its various forms is often put at risk seems an urgent matter to us. The concern for the ways in which the democratic discourse is put at risk in many different parts of the word is registered outside the design community (for instance by philosophers such as Noam Chomsky), as well as within (see for instance Manzini’s and Margolin’s call Design Stand Up (http://www.democracy-design.org). Therefore, the need to articulate a discussion on this difficult matter, and to find a common vocabulary we can share to talk about it. One of the difficulties encountered for instance when discussing this issue, is that the word “democracy” is understood in different ways, in relation to the traditions and contexts in which it is framed. Philosophically speaking, there are diverse discourses on democracy that currently inspire design researchers and theorists, such as Arendt, Dewey, Negri and Hardt, Schmitt, Mouffe, Rancière, Agamben, Rawls, Habermas, Latour, Gramsci, whose positions on this topic are very diverse. How can these authors guide us to further articulate this discussion? In which ways can these philosophers support and enrich design’s innovation discourses on design and democracy, and guide our thinking in addressing sensitive and yet timely questions, such as what design can do in what seems to be dark times for democracy, and whether design can possibly contribute to enrich the current democratic ecosystems, making them more strong and resilient?

In Quest of a Second Boom

2018 ◽  
Vol 11 (1-2) ◽  
pp. 257-278 ◽  
Author(s):  
Shirzad Azad
Keyword(s):  
Foreign Policy ◽  
Middle East ◽  
Crucial Role ◽  
Gulf Cooperation Council ◽  
East Region ◽  
Personal Motivation ◽  
Policy Measures ◽  
The Republic ◽  
Middle East Region ◽  
Different Parts

In spite of her troubled presidency at home and premature, ignominious exit from power, Park Geun-hye made serious attempts to bolster the main direction of the Republic of Korea’s (ROK) foreign policy toward the Middle East. A collaborative drive for accomplishing a new momentous boom was by and large a dominant and recurring theme in the Park government’s overall approach to the region. Park enjoyed both personal motivation as well as politico-economic justifications to push for such arduous yet potentially viable objective. Although the ROK’s yearning for a second boom in the Middle East was not ultimately accomplished under the Park presidency, nonetheless, the very aspiration played a crucial role in either rekindling or initiating policy measures in South Korea’s orientation toward different parts of a greater Middle East region, extending from the Gulf Cooperation Council (GCC) to Morocco.

Alcohol Absorption Rate from Different Parts of the Gut

1968 ◽  
Vol 29 (2) ◽  
pp. 308-312
Author(s):  
Ronald G. Elmslie ◽  
Nanette Harvey
Keyword(s):  
Absorption Rate ◽  
Different Parts
Sign in / Sign up

Export Citation Format

Share Document