  Woody
bamboos are the largest representatives of the botanical family
of the grasses. Many of them have a peculiar life cycle: they
grow for many years and flower only once in their lives. Then
they die, producing seeds for the next generation. In many
species, these flowering events occur en masse, apparently
according to an internal clock. As a result, every thirty years,
for example, in a given place, all plants of a given species
flower. These cycles differ in different species of bamboo, and
they have important consequences for several birds that depend
on the food resources offered by bamboos.
In Misiones, there are five fairly widespread species of
native bamboos. (There are other species, but they are rare and
local). The five widespread species are Takuarembo (Chusquea
ramosissima), Pitinga (Chusquea tenella), Takuapi (Merostachys
claussenii), Yatevo (Guadua trinii) and Takuarusu (Guadua
chacoensis).
Our research consists of finding out which species of birds
use which species of bamboo, and how they use them. We observe
and tape-record birds in different species of bamboo, noting the
characteristics of the bamboo stands (e.g., density, maturity,
seed production).
We divide bamboo specialist birds into two categories: those
that eat insects (insectivores) and those that eat bamboo seeds
(granivores). As we saw before, bamboos flower only after many
years, and then they die. These long cycles have different
consequences for insectivores and granivores. When the bamboo
flowers and dies, insectivorous bamboo specialists like the
White-bearded Antshrike (Biatas nigropectus) temporarily lose
much of their habitat. But granivorous bamboo specialists like
the Blackish-blue Seedeater (Amaurospiza moesta), the Sooty
Grassquit (Tiaris fuliginosus) and the Temminck’s Seedeater
(Sporophila falcirostris), obtain, after many years, their most
prized resource: bamboo seeds. Logically, bamboo specialist
granivores are harder to study than bamboo specialist
insectivores. Bamboo specialist granivores pursue an ephemeral
resource, while insectivores live a more stable life in the same
place. We have been fortunate that our time in Misiones has
coincided with flowering events of three bamboo species:
Takuarembo, Takuapi, and Takuarusu. We found that these
different species of bamboos support different species of
insectivorous birds, and their seeds attract different species
of granivores.
Fotografías: todas las
fotos fueron tomadas por Nacho Areta y Kristina Cockle, salvo
las de la Reinamora Enana (A. moesta) que fueron tomadas por
Jorge Spinuzza.
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