The UK Nest Record Scheme: its value for science and conservation

Capsule A review of its methodology, analytical procedures and uses.

Aims To provide a comprehensive review of the UK Nest Record Scheme (NRS), its methodology and value to science and conservation.

Methods We reviewed the history of the development and current methodology used in the analysis of NRS data in the scientific literature and unpublished documents and from our personal knowledge.

Results The British Trust for Ornithology's (BTO's) NRS is the largest, longest running and most highly computerized such scheme in the world. Advanced and efficient techniques of data gathering, data capture and analysis are used. It was founded in 1939 to provide information on the breeding biology of birds, but has since developed into a key component of the overall monitoring strategy for birds in the UK. A range of specialized analytical methods is available for NRS data and potential biases need careful treatment. More than 250 scientific publications have used NRS data to describe aspects of basic breeding biology and performance, to study the population dynamics of bird populations and to investigate the demographic causes of bird population declines in the UK.

Conclusions Extensive long-term monitoring schemes, such as the NRS, that collate large historical data sets will become increasingly valuable for monitoring the impact of environmental change. While aspects of the NRS, its recording methods, data capture and analysis can be developed further, the scheme will continue to advance our understanding of both the impacts of new environmental stresses in the UK and the effectiveness of new conservation measures in the wider countryside. This has been amply demonstrated by its use for exploring the impacts of global climate change on the UK's avifauna.     

Population dynamics of Macaca sylvanus in Algeria: An 8-year study

The demography and dynamics of two groups, one living in an evergreen cedar-oak forest (Tigounatine) and the other, in a deciduous oak forest (Akfadou) in Algeria, were studied from 1982 to 1990. Group size fell within the range of other wild groups except for the Tigounatine group when it reached 88 individuals before splitting into three new independent groups. The structure of the studied groups, except one which was temporarily “one male,” was comparable to that of other groups of Barbary macaques. There were 43–50% of immatures on average depending on the group. The sex ratio (M:F) of the sexually mature animals was relatively balanced (1:0.9–1.2). The mean age of primiparous females was 5.5 years in Tigounatine and 5.3 in Akfadou; the rate of reproduction of sexually mature females was 0.56 and 0.63, respectively, while the infant mortality rate was 0.23 and 0.38, respectively. Great interannual variations occurred at both sites. The differences between natality and mortality induced a higher intrinsic mean annual increase for the Tigounatine group (14.6%) than for the Akfadou group (4.8%). The rate of intergroup transfers was not correlated with the increase in group size. Integration of male immigrants did not lead to the departure of resident males. Conversely, fission process promoted a substantial increase in the number of transfers in Tigounatine. The period presenting the greatest risk of infant mortality was the summer dry period, in both habitats. Wide interannual variations occurred in the availability of two staple foods for monkeys: caterpillars and acorns. The cumulative effects of a low acorn supply during the gestation period (autumn) and a low caterpillar supply during the beginning of the following nursing period (spring) led to a temporary increase in infant mortality. © 1993 Wiley-Liss, Inc.     

To eject or to abandon? Life history traits of hosts and parasites interact to influence the fitness payoffs of alternative anti‐parasite strategies

Hosts either tolerate avian brood parasitism or reject it by ejecting parasitic eggs, as seen in most rejecter hosts of common cuckoos, Cuculus canorus, or by abandoning parasitized clutches, as seen in most rejecter hosts of brown‐headed cowbirds, Molothrus ater. What explains consistent variation between alternative rejection behaviours of hosts within the same species and across species when exposed to different types of parasites? Life history theory predicts that when parasites decrease the fitness of host offspring, but not the future reproductive success of host adults, optimal clutch size should decrease. Consistent with this prediction, evolutionarily old cowbird hosts, but not cuckoo hosts, have lower clutch sizes than related rarely‐ or newly parasitized species. We constructed a mathematical model to calculate the fitness payoffs of egg ejector vs. nest abandoner hosts to determine if various aspects of host life history traits and brood parasites’ virulence on adult and young host fitness differentially influence the payoffs of alternative host defences. These calculations showed that in general egg ejection was a superior anti‐parasite strategy to nest abandonment. Yet, increasing parasitism rates and increasing fitness values of hosts’ eggs in both currently parasitized and future replacement nests led to switch points in fitness payoffs in favour of nest abandonment. Nonetheless, nest abandonment became selectively more favourable only at lower clutch sizes and only when hosts faced parasitism by a cowbird‐ rather than a cuckoo‐type brood parasite. We suggest that, in addition to evolutionary lag and gape‐size limitation, our estimated fitness differences based on life history trait variation provide new insights for the consistent differences observed in the anti‐parasite rejection strategies between many cuckoo‐ and cowbird‐hosts.     

WHAT DETERMINES FITNESS WHEN DISPERSAL IS LIMITED?

Simple evolutionary models typically assume a homogeneous environment in which all individuals have equal access to resources. However, when dispersal is limited this assumption is unlikely to correspond to reality. Instead, the offspring of relatively fecund parents can be expected to find that resources are scarce because of competition from their relatively large number of siblings. We show that these factors lead to selection for decreased variation in the number of offspring produced. We investigate the relationship between fitness and variation in fertility for a variety of different circumstances. Our results indicate that, in some cases, selection for reduced variation in fertility can be very substantial.