Life and Death in the Fast Lane: Demographic Consequences of Road Mortality in the Florida Scrub‐Jay

Abstract

We examined the demographic consequences of road mortality in the cooperatively breeding Florida Scrub‐Jay (Aphelocoma coerulescens), a threatened species restricted to the oak scrub of peninsular Florida. Between May 1986 and July 1995 we monitored the survival and reproductive success of a color‐banded population of jays along a two‐lane highway at Archbold Biological Station. Annual mortality of breeding adults was 0.38 on road territories, significantly higher than the rate of 0.23 for breeders on nonroad territories. High mortality on road territories appeared to be a direct result of automobile traffic per se and not a consequence of road‐induced changes in habitat characteristics. Mortality was especially high for immigrants without previous experience living along the road: in their first two years as breeders on road territories, naive immigrants experienced annual mortality of 0.50 and 0.45. From year 3 onward, however, annual mortality dropped to 0.29, not significantly different from the rate for birds on nonroad territories. This experience‐dependent decline in road mortality could be caused either by surviving jays learning to avoid automobiles or by selective mortality operating through time (demographic heterogeneity). Proximity to the road had no effect on nesting success beyond its indirect effects on breeder experience and group size. Because the mortality of 30‐ to 90‐day‐old fledglings was significantly higher on road territories than on nonroad territories, however, breeder mortality greatly exceeded production of yearlings on road territories. Roadside territories therefore are sinks that can maintain populations of Florida Scrub‐Jays only via immigration. Because Florida Scrub‐Jays do not avoid roadside habitats and may even be attracted to them, road mortality presents a difficult challenge for the management and conservation of this threatened and declining species.

Road Effects on Food Availability and Energetic Intake in Florida Scrub-Jays (Aphelocoma coerulescens)

“…Although high-speed paved roads are known to have pronounced negative impacts on the survival of Florida Scrub-Jays (Mumme et al 2000), the present association between roads and juvenile mortality cannot be explained by road kill; sand roads and fire lanes within Archbold are private, unpaved, and lightly travelled by low-speed vehicles that pose no threat to jays. Instead, we suspect that roads and fire lanes facilitate patrolling movements by the numerous mammalian and snake predators in this habitat, and that juvenile jays tend to be more conspicuous and vulnerable when foraging or roosting along roads.…”

Spatio-temporal variation of roadkills show mass mortality events for amphibians in a highly trafficked road adjacent to a national park, Costa Rica

“…The main nesting peak takes place from April through June (Stiles & Skutch, 1989), so it is possible that dispersing individuals following fledging accounted for the deaths. There is evidence that young, naïve individuals are more likely to get killed on roads than more experienced adults (Mumme, Schoech, Woolfenden, & Fitzpatrick, 2000). However, we could not verify this as five out eight dead birds during December and January were so badly damaged that they could not be identified.…”

Intentional Snake Road-Kill: A Case Study using Fake Snakes on a Brazilian Road

“…Among road impacts, vehicle collisions are the leading cause of direct mortality of animal populations [2][3][4]. In certain circumstances, a severe reduction in the population size of species subject to high road-kill rates results in a subsequent biodiversity loss [5].…”