Food availability and breeding season as predictors of geophagy in Amazonian parrots

Abstract

Geophagy, the consumption of soil, is common in many species, but the drivers of geophagy are not well understood. The best-studied example of avian geophagy is the parrots of the western Amazon Basin, but even here, there is debate over what drives the behaviour. There are two possible explanations: (1) extra nutritional demands of reproduction drive an increase in geophagy, which would predict that geophagy should be highest during the breeding season, and (2) consumption of naturally toxic plant foods increases the need for the toxin protection effects of soil, which would predict that geophagy should be highest when food availability is low and animals are forced to consume more toxic foods. We used long-term data from lowland Amazonia to compare seasonal fluctuations in rainfall, food availability, parrot breeding and parrot geophagy, and conducted novel tests of these hypotheses. Our analyses of annual patterns suggested that seasonal changes in rainfall drive plant fruiting, the resulting food availability patterns drive the timing of parrot breeding, and breeding drives seasonal patterns of geophagy. Surprisingly, chicks of the largest psittacine species fledged as food supplies approach their annual lows, suggesting that future climatic changes that alter peaks in food availability could have unexpected impacts on the reproduction of large psittacines in this system. Our tests found no evidence to support the toxin-protection hypothesis. Instead, we found that the peak of geophagy occurred during species' breeding seasons, which strongly supports the supplemental nutrients hypothesis. Our findings join a growing body of biochemical, physiological, behavioural, ecological and biogeographical evidence suggesting that a need for sodium is driving soil consumption in this classic model system of avian geophagy.

Satellite telemetry reveals complex migratory movement patterns of two large macaw species in the western Amazon basin

“…During the non-breeding season, birds that migrated expanded their home ranges and included areas as far as 160 km from their nests. This movement away from the nesting area was not a surprise due to the sharp drop in food supplies throughout our study region during the non-breeding season (Adamek 2011, Lee et al 2014, Brightsmith et al 2018. This finding also supports the previously published hypothesis that seasonal variation in abundance and clay lick use in the Tambopata region are driven in large part by birds moving in and out of the area (Brightsmith 2004, Brightsmith et al 2018.…”

“…For migratory individuals, both species showed abrupt transitions from the breeding range to the non-breeding range with single movements of over 10 km and both departed from the breeding range and returned to the breeding range on the same day on average. These similarities in breeding home range size and movements may be because both species have relatively high dietary overlap during the breeding season (Adamek 2011, Lee et al 2014) and both may respond in similar ways to the seasonal drop in food supplies at the end of breeding (Brightsmith et al 2018, Carrara et al 2019.…”

“…We use Argos satellite telemetry collars developed for large macaws (Boyd and Brightsmith 2013) to determine the ranging patterns of Scarlet (Ara macao) and Blue-and-yellow (Ara ararauna) Macaws during the breeding and non-breeding seasons in the lowlands of the Tambopata region of southeastern Peru. In this region, both species show large seasonal variation in abundance and soil consumption at clay licks (Renton 2002, Brightsmith et al 2018. While neither species completely disappears from the area, both species drop greatly in abundance shortly after chicks fledge in March, then abundance increases again during the middle of the dry season beginning in July (Brightsmith et al 2018, and DJB unpublished data).…”

Satellite Telemetry of Blue-Throated Macaws in Barba Azul Nature Reserve (Beni, Bolivia) Reveals Likely Breeding Areas

“…In Barba Azul, some Motacú patches are nearly monodominant, possibly due to past human influences, and can produce fruit nearly all year [25,35], so that the birds there do need not to move far for feeding. In contrast, in Tambopata, Peru, food abundance shows large seasonal fluctuations [56] and feeding trees are often scattered in a more diverse forest matrix. The flight range of BTMs that left Barba Azul suggests that the species is able to fly similar distances as other macaws.…”

Inferring the identifying features underlying association preferences in wild mixed species parrot groups

“…Individual parrots make decisions about when to visit the clay wall, where to land on the wall, and when to depart. In this system, clay consumption is thought to provide necessary nutrients such as sodium, which are otherwise rare in the tropical environment [5]. Individuals interact frequently with other species at the clay, often by responding to alarm calls and aggressing against other species.…”