Demography of an Increasing Population of Sparrowhawks

Wyllie, I.; Newton, Ian

doi:10.2307/5412

Cited by 45 publications

(43 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Balbontın et al (2003), proposed two possible causes of an increase in immature breeders. First, it could be due to an increase in mortality rate, either immature or adult (Valverde, 1960;Newton, 1979;Novelletto and Petretti, 1980;Ratcliffe, 1980;Steenhof et al, 1983) or it could be due to an increase in the availability of resources such as nest sites or food supply, such as occurs when populations are increasing (McGowan, 1975;Newton, 1976;Wyllie and Newton, 1991;Brommer et al, 1998). Evidence from our study supported the hypothesis that a decrease in age at first breeding was due to an increase in adult mortality rate, as shown by the relationship between the numbers of adult eagles found dead and the proportion of immature breeders.…”

Section: Discussionmentioning

confidence: 99%

The proportion of immature breeders as a reliable early warning signal of population decline: evidence from the Spanish imperial eagle in Doñana

Ferrer

Penteriani

Balbontı́n

et al. 2003

Biological Conservation

View full text Add to dashboard Cite

Methods to evaluate population trends have recently received particular attention because of perceived declines in several species during the 20th century. We investigated whether age at first breeding could be used as an ''early warning signal'' to detect possible changes in population trends in long-lived species with deferred maturity using data from the Spanish imperial eagle (Aquila adalberti) population in Donana National Park (Spain). This bird of prey is an endangered species that has suffered a rapid decline in this population during the last 10 years. As a result of our 27-year monitoring ) study, we detected that an increase in immature breeding birds occurred before population decline became evident. The proportion of immature-plumaged breeders in the population was significantly higher during the period of decline than during the period of stability. In our case, more than 10% of immature breeders can be considered as an ''early warning signal'' that anticipates population decline. Owing to the ignorance of this warning signal, urgent actions for the recovery of this eagle population started 10 years later than necessary, and when population size had been reduced.

show abstract

Section: Discussionmentioning

confidence: 99%

The proportion of immature breeders as a reliable early warning signal of population decline: evidence from the Spanish imperial eagle in Doñana

Ferrer

Penteriani

Balbontı́n

et al. 2003

Biological Conservation

View full text Add to dashboard Cite

show abstract

“…Wyllie & Newton, 1991). Little information is available on the age composition of floaters (but see Sergio, Blas & Hiraldo, 2009), although it is generally accepted that nonbreeding components of populations are mainly composed of juveniles (Newton, 1991(Newton, , 1992Rohner, 1996).…”

Section: Density-dependent Regulation Of Bird Populations and The Allmentioning

confidence: 99%

Floater strategies and dynamics in birds, and their importance in conservation biology: towards an understanding of nonbreeders in avian populations

Penteriani

Ferrer

Delgado

2011

Animal Conservation

154

159

View full text Add to dashboard Cite

Over the past 40 years, the study of animal populations has shifted from a relatively simple science that assumed the most crucial regulating mechanisms were the intrinsic properties of breeders, to a more complex and refined discipline that reflects a greater understanding of populations and their dynamics. Part of this shift has been the explicit recognition of the importance of a previously overlooked nonbreeding component of animal populations, the so-called floaters.Here we review and discuss the various effects that pools of floaters can have on the structure, dynamics and persistence of bird populations. Under some circumstances floaters can be both active intruders that can alter the breeding performance and behavioural traits of territory owners, as well as secretive presences reducing the extinction risk of populations. Floaters are crucial elements in conservation biology, and knowledge of their behaviour and dynamics in avian communities can be a key factor in the success of conservation strategies. Firstly, larger pools of floaters are associated with more stable breeding populations, even in cases where breeding output could be impacted through interference by floaters. Secondly, the effects of habitat loss and mortality rates are frequently ignored in areas where floaters settle, and consequently conservation measures tend to overlook these sites, potentially leading to increased risks of mortality among floaters. Thirdly, because an increase in the proportion of juveniles in the breeding component of a population may be because of increased pre-adult and/or adult mortality rates, a change in the age of breeders has the potential to function as a warning of an imminent decline in breeding populations. Most population studies have only considered the breeding components of animal populations, so it is time now to focus attention on the floater component, wherein the solution to many conservation issues may be found.

show abstract

“…Populations of affected bird species then recovered at varying rates (Wyllie and Newton 1991;Newton and Wyllie 1992;Newton 1998;Banks et al 2010). By 2000, the British population of peregrines had fully recovered naturally from the deleterious effects of organochlorine pesticides, although reductions in territory occupancy rates were subsequently reported from parts of Scotland, associated with an increase in human persecution (Banks et al 2010).…”

Section: Introductionmentioning

confidence: 97%

Demography of population recovery: survival and fidelity of peregrine falcons at various stages of population recovery

Smith¹,

Murillo‐García

Hostetler

et al. 2015

Oecologia

View full text Add to dashboard Cite

Factors influencing vital demographic rates and population dynamics can vary across phases of population growth. We studied factors influencing survival and fidelity of peregrine falcons in south Scotland-north England at two stages of population growth: when the population was recovering from pesticide-related declines and density was low, and when it had largely recovered from pesticide effects and density was high. Fidelity was higher for: adults and subadults than for juveniles, females than for males, and juveniles and adults during the low-density than during the high-density study period. Survival was age specific, with lower survival for juveniles than for older birds (juveniles, 0.600 ± SE 0.063; subadults, 0.811 ± 0.058; adults, 0.810 ± 0.034). Furthermore, there was some evidence that survival was generally lower for all age classes during the low-density period than during the high-density period, possibly due to a chronic, persistent effect of organochlorine pesticides as the population recovered. Evidence for a density-dependent effect on survival was weak, but a negative effect of density on fidelity of juveniles (dispersing age class) during the recovery phase suggests density-dependent dispersal when the population was increasing. Our results show how population density can influence demographic parameters differently and how such influences can vary across phases of population growth.

show abstract

Demography of an Increasing Population of Sparrowhawks

Cited by 45 publications

References 10 publications

The proportion of immature breeders as a reliable early warning signal of population decline: evidence from the Spanish imperial eagle in Doñana

The proportion of immature breeders as a reliable early warning signal of population decline: evidence from the Spanish imperial eagle in Doñana

Floater strategies and dynamics in birds, and their importance in conservation biology: towards an understanding of nonbreeders in avian populations

Demography of population recovery: survival and fidelity of peregrine falcons at various stages of population recovery

Contact Info

Product

Resources

About