Comparing bird assemblages in large and small fragments of the Atlantic Forest hotspots

Abstract

The Atlantic Forest (AF) is one of the Wve most threatened and megadiverse world hotspots. It is arguably the most devastated and highly threatened ecosystem on the planet. The vast scope of habitat loss and extreme fragmentation in the AF hotspots has left intact very few extensive and continuous forested fragments. We compared bird assemblages between small (<100 ha) and large (>6,000 ha) forest remnants, in one of the largest AF remnants in Argentina. We performed 84 point-counts of birds in four large fragments (LF) and 67 points in 25 small fragments (SF). We recorded 4,527 bird individuals belonging to 173 species; 2,632 belonging to 153 species in LF and 1,897 in 124 species in SF. Small fragments suVered a signiWcant loss of bird richness, mainly forest dependent species, but the birds abundance did not decrease, due to an increase in abundance of forest independent and semi-dependent bird species (edge and non forest species) that beneWt from forest fragmentation. The bird guilds of frugivores, undestory, terrestrial and midstory insectivores, nectarivores and raptors, and the endemic species of AF were area sensitive, decreasing signiWcantly in richness and abundance in the SF. Terrestrial granivores were the only guild positively aVected by forest fragmentation, containing mainly edge species, which forage in open areas or borders including crops. Our 1 C validate the hypothesis on pre-adaptation to human disturbances in the bird communities of AF. On the contrary, we observed that forest dependent, endemic and several sensitive bird guilds were strongly aVected by fragmentation, putting in evidence the vulnerability to the fragmentation process and the necessity to conserve large remnants to avoid reduction of the high biodiversity of AF birds.

No evidence for widespread bird declines in protected South American forests

“…South America loses about 2.5 million ha of humid tropical forest per year to deforestation (Achard et al 2002), with strong and direct impacts on forest birds at the local and regional scale (e.g. Ribon et al 2003;Lees and Peres 2006;Stouffer et al 2006Stouffer et al , 2009Giraudo et al 2008). The most important step to conserve forest bird communities in South America remains the protection of large tracts of native forest.…”

The effect of windthrow and its management on breeding bird communities in a managed forest

“…The points were sampled in random order. During the 10-min counts, I recorded all individuals heard or seen up to a 100 m circumference (which is the radius often used in bird monitoring schemes- Dunford and Freemark 2005;Giraudo et al 2008). In order to exclude migrants, birds in flight were not recorded.…”

The effect of contrasting management types on two distinct taxonomic groups in a large-scaled windthrow

“…The points were sampled in a random order. During each 10-min count, we recorded all the individuals heard and seen within a radius of 100 m (Giraudo et al 2008). In order to exclude migrants, we did not record birds flying above the canopy since they do not use windthrow being sampled (Faccio 2003).…”