Population dynamics of ducks is a complex process influenced by both biotic and abiotic factors, and good understanding about the mechanisms behind this process is needed not only for the management of duck harvest but also for the conservation of wetland, which is under threat in the face of land change and climate warming. Basic time series analysis techniques, such as correlogram, partial correlogram and periodogram, cluster analysis and partial least squares regression (PLSR) are applied to the long-term breeding population data gathered by Waterfowl Breeding Population and Habitat Survey and monthly weather data from Environment Canada in order to explore the pattern in the duck abundance data and the effect of local weather on population dynamics of ducks. Results of above analysis show that the duck abundance of previous years has short but strong correlation with the duck abundance of following years suggesting a large part of variability in duck abundance is explained by the abundance of previous years, especially that of last year. There is also clear periodic pattern in the duck abundance data, but the length of the cycle varies both for duck species and ecozones suggesting separating duck species and ecozones for analysis is necessary. The effects of weather on duck populations appear weak or absent in most PLSR models; this is consistent with previous studies. More detailed information, such as age structure of the duck populations and interspecific interactions, will be needed for future modeling. Among the small number of PLSR models exhibiting the weather effect, results suggest potential mechanisms, such as the impact of weather on recharge and discharge of wetland basins and nest failure caused by flooding.

Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-23Bitstream added on 2014-06-13T19:53:27Z : No. of bitstreams: 1 maciel_ga_me_ift.pdf: 510710 bytes, checksum: febf0f526cd25a0f287f0521556976fc (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Predação intraguilda é um tipo de interação muito comum entre as espécies e pode influenciar fortemente na composição das comunidades ecológicas. Ela ocorre quando dois consumidores que compartilham de um mesmo recurso, e portanto competem, também apresentam comportamento predatório entre si. O consumidor que preda o seu competidor é frequentemente chamado de predador intraguilda, enquanto aquele que é predado é conhecido como presa intraguilda. Nesse trabalho nós investigamos alguns aspectos teóricos sobre esse tipo de interação. Primeiramente analisamos um experimento com ácaros predadores que foi realizado para testas as predições da teoria sobre padrões de exclusão em um gradiente de produtividade. Embora esse experimento foi cuidadosamente projetado para testar afirmações da teoria, seus resultados não concordam com ela. Utilizando um modelo bem simples para predação intraguilda que serve como uma representação daquele sistema, nós mostramos que: se levarmos em conta a dinâmica durante os transientes, e não apenas os resultados no equilíbrio, em que a teoria usual se baseia, e considerarmos que quando uma população atinge níveis muito baixos corresponde a uma extinção na realidade, os resultados experimentais concordam com a teoria. Em seguida nós estudamos questões que dizem respeito a influência dos diferentes estágios de vida dos indivíduos para a dinâmica da predação intraguilda. Nós introduzimos um modelo com estrutura de estágio em ambos os consumidores e consideramos a predação ocorrendo apenas dos adultos do predador intraguilda sobre os juvenis da presa intraguilda. Tem-se acreditado que essa interação dependente de estágio pode ter grandes efeitos sobre a dinâmica, uma vez que a pressão predatória sobre a presa intraguilda é reduzida... / Intraguild predation is a widespread interaction between species and can strongly influence communities composition. It occurs when two consumers which share a common resource, and hence compete, also engage into predation. The consumer which can prey on its competitor is often referred to as the intraguild predator while the other is called intraguild prey. In this work we investigate some theoretical aspects about these interactions. First we analyse an experiment with predatory mites which was carried to test patterns of exclusion along a productivity gradient, predicted by theory. Although this experiment was carefully designed to test the theoretical assertions, their results do not agree with theory. Through a very simple model for intraguild predation which serves as a representation of that system, we show that: if the short-term dynamics is taken into account rather than only equilibrium states, in which the usual theory is based, and we consider that populations that attain levels very close to zero are extinct, experimental results meet theory. Then we study questions concerning the influence of different life stages of individuals on the dynamics of intraguild predation. We introduce a model with stage structure in both consumers and consider predation occurring only from adults of the intraguild predator on juveniles of the intraguild prey. This stage dependent interaction was believed t ohave great effects on the dynamics, once predation pressure on the intraguild prey is reduced, and has been proposed as one feature that could promote coexistence. We check the outcomes of the system along a productivity gradient and show that stage structure do not induce great qualitative changes on the dynamics and the more likely resulting dynamics continues being the extinction of one of the consumers... (Complete abstract click electronic access below)

No description available.

No description available.

No description available.

No description available.

No description available.

No abstract available. / Thesis (Ph.D)-University of Durban-Westville, 2003.

The purpose of this study was to determine the effect of substrate levels and different types of substrates on population changes of mixed cultures of Serratia marcescens and Saccharomyces cerevisiae, as compared to pure cultures.

Storm-created nesting habitat and low wave energy moist sediment habitat (MOSH), such as intertidal sandflats, have long been considered important to the recovery of the piping plover (Charadrius melodus), a federally threatened shorebird. Beach renourishment is a common practice on the U.S. Atlantic Coast for the protection of human property from storms, but it also prevents normal MOSH formation. We examined factors limiting piping plover nesting pair density and reproductive output on Atlantic Barrier Islands, 2001-2004, including one site that had been breached by a storm in 1992, and subsequently repaired and renourished by the U.S. Army Corps of Engineers. We also investigated the short-term impact of beach renourishment at these sites. Number of pairs at a site increased with beach area. Pair density increased with MOSH availability at the site level. Home range size increased as the distance from plover nests to MOSH increased. Home range size was smaller for plovers with higher foraging rates in the territory-establishment period, but this effect was most likely independent of distance to MOSH. Reproductive output was not apparently related to availability of MOSH to adults or broods, and was limited by predation. Habitat widths, prey abundance, and brood habitat selection changed at two of our sites after renourishment. However, similar changes occurred in reference areas. Other research shows that in addition to long-term loss of storm-created features, beach stabilization can lead to loss of habitat and low reproductive success due to human development and an increased presence of introduced predators. Management for recovery of this species should thus include permitting natural storm-mediated habitat creation to occur where feasible. However, since we found no direct negative short-term impact of renourishment on prey or habitat availability, habitat restoration via renourishment of eroded beaches could be a viable strategy for plover recovery, if negative indirect short and long-term effects are mitigated. Restoration projects should include restoration or creation of MOSH adjacent to nesting habitat, because MOSH attracts a high density of pairs and to offset long-term loss of storm-created habitat. Human disturbance and predation must also be controlled at restoration sites. / Ph. D.