Sex and age dependency of wing patch size in Brown Skuas

2003 ◽  
Vol 103 (1) ◽  
pp. 37-41 ◽  
Author(s):  
Steffen Hahn ◽  
Hans-Ulrich Peter
Keyword(s):  



The Auk ◽  
2002 ◽  
Vol 119 (2) ◽  
pp. 566-572 ◽  
Author(s):  
Piotr G. Jaboński ◽  
Piotr Matyjasiak

Abstract Recent studies reveal that asymmetries of bilateral characteristics may reflect poor condition, serving as an honest indicator of mate quality. We asked whether bilateral asymmetry might also influence behavior during aggressive intrasexual contests. In the Common Chaffinch (Fringilla coelebs), bilateral, white wing patches (epaulettes) are used during aggressive interactions. We recorded responses of males to model intruders placed on territories of focal males, to determine whether their response to asymmetry varied with wing-patch size. When epaulettes were large, models with asymmetric patches elicited more rapid, directed aggression from the territory owners than did models with symmetric patches. We observed no such difference when model intruders had small epaulettes. If asymmetry of epaulettes in chaffinch males indicates poor condition, our results suggest higher costs of aggressive signaling for individuals in poor than good condition.







2020 ◽  
Vol 648 ◽  
pp. 111-123
Author(s):  
C Layton ◽  
MJ Cameron ◽  
M Tatsumi ◽  
V Shelamoff ◽  
JT Wright ◽  
...  

Kelp forests in many regions are experiencing disturbance from anthropogenic sources such as ocean warming, pollution, and overgrazing. Unlike natural disturbances such as storms, anthropogenic disturbances often manifest as press perturbations that cause persistent alterations to the environment. One consequence is that some kelp forests are becoming increasingly sparse and fragmented. We manipulated patch size of the kelp Ecklonia radiata over 24 mo to simulate persistent habitat fragmentation and assessed how this influenced the demography of macro- and microscopic juvenile kelp within the patches. At the beginning of the experiment, patch formation resulted in short-term increases in E. radiata recruitment in patches <1 m2. However, recruitment collapsed in those same patches over the extended period, with no recruits observed after 15 mo. Experimental transplants of microscopic and macroscopic juvenile sporophytes into the patches failed to identify the life stage impacted by the reductions in patch size, indicating that the effects may be subtle and require extended periods to manifest, and/or that another life stage is responsible. Abiotic measurements within the patches indicated that kelp were less able to engineer the sub-canopy environment in smaller patches. In particular, reduced shading of the sub-canopy in smaller patches was associated with proliferation of sediments and turf algae, which potentially contributed to the collapse of recruitment. We demonstrate the consequences of short- and longer-term degradation of E. radiata habitats and conclude that habitat fragmentation can lead to severe disruptions to kelp demography.



1985 ◽  
Vol 19 (4) ◽  
pp. 129A-129A
Author(s):  
Thomas S Klitzner ◽  
William F Friedman


2021 ◽  
Vol 11 (1) ◽  
pp. 26
Author(s):  
João Leitão ◽  
João Capucho

This empirical study analyses the effects of institutional, economic, and socio-economic determinants on total entrepreneurial activity in the contexts of developed and developing countries. It fills a gap in the literature, regarding the lack of empirical studies about the relationships among entrepreneurial activity, corruption, commercial freedom, economic growth, innovativeness, inward foreign direct investment, unemployment, households, and non-profit institutions serving households (NPISHs)’ final consumption expenditure, age dependency ratio, education index, and life expectancy at birth. The empirical application uses annual panel data for the 2003–2018 period, with a total sample of 21 countries, analysed in a two-stage empirical application, including preliminary analysis and a quantile regression model. New empirical evidence is provided, revealing a significantly positive role played by commercial freedom, innovativeness, inward foreign direct investment, households, and NPISHs’ final consumption expenditure and education on entrepreneurial activity. Corruption, unemployment, age dependency ratio, and life expectancy at birth have a significantly negative influence on entrepreneurial activity. In terms of implications, greater government control is recommended, in order to foster the quality of nations’ institutional environment. Additionally, suggested is the launch of new incentives to stimulate research and development activities aimed at registering international patents with a global impact, sourced from new ventures and transnational collaboration.



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