Multiple species of cuckoos are superior predictors of bird species richness in Asia

Abstract

Abstract. The abundance and the presence of common cuckoos Cuculus canorus have been shown to predict species richness of birds across Europe, while there are no such analyses available for other continents where species richness of parasitic cuckoos is larger. Here, we tested whether species richness of birds increased with the number of cuckoo species in two study areas in China and one in Japan. We also tested whether species richness of birds can be predicted by the number of cuckoo individuals. Furthermore, we compared the strength of association between overall bird species richness and species richness of cuckoos, Paridae, Corvidae, and birds of prey. This is the first study demonstrating that cuckoo species richness is more strongly associated with overall bird species richness than richness of species belonging to other families, and rather than occurrence of a single cuckoo species, as already demonstrated for the common cuckoo in Europe. The number of cuckoo species was positively associated with both non-host and host species richness. We found evidence of the number of cuckoo species being associated with species richness of birds independently of country and year, while abundance of individual cuckoos was not a statistically significant predictor. Furthermore, we showed that richness of host species is strongly positively correlated with overall bird species richness in both countries. This implies that the high species richness of cuckoos in South-East Asia is a reliable predictor of overall bird species richness.

Titmice are a better indicator of bird density in Northern European than in Western European forests

“…Even though many of the randomly drawn species groups performed better as an indicator than titmice, in France, the species sets included in those random species groups cannot be observed as easily as titmice. Similarly, other commonly used indicator bird species groups, such as woodpeckers (Menon & Shahabuddin, 2021; Mikusiński et al, 2001) or cuckoos (Møller et al, 2017), are relatively less abundant and diverse, and more habitat specialized than many titmouse species, potentially making them less suitable indicators for forest bird abundances. Titmice have many features of a suitable ecological indicator group: cost‐efficient observations, well‐known biology, conspicuous behavior, almost global distribution (Caro & O'Doherty, 1999; del Hoyo et al, 2007; Gill et al, 2005; Landres et al, 1988), and ecological traits broadly overlapping with those of a wide range of the target species.…”

“…The use of indicator species to estimate target species occurrence or abundance can be based on similar responses to abiotic factors (Caro & O'Doherty, 1999 ; Sætersdal et al, 2003 ) or biotic associations between the indicator and target species groups (Møller et al, 2017 ; Sergio et al, 2006 ). Even though negative interspecific interactions, such as competition, can negatively affect species co‐occurrence and abundance (Forsman et al, 2008 ; Goldberg & Barton, 1992 ), shared habitat preference and positive interspecific interactions may promote co‐occurrence of species and create aggregations of individuals (Basile et al, 2021 ; Forsman et al, 2009 ).…”

“…Our study system is the European forest bird community, where we study whether the conspicuous and easy‐to‐identify species of titmice (family Paridae) could indicate density of breeding forest birds. In Asia, species richness of titmice has been found to be a poor indicator of overall bird species richness (Møller et al, 2017 ). However, Møller et al ( 2017 ) observed a maximum of two titmouse species, while titmice are more diverse in Europe (del Hoyo et al, 2007 ).…”

“…In Asia, species richness of titmice has been found to be a poor indicator of overall bird species richness (Møller et al, 2017 ). However, Møller et al ( 2017 ) observed a maximum of two titmouse species, while titmice are more diverse in Europe (del Hoyo et al, 2007 ). Additionally, other bird species groups, such as woodpeckers (family Picidae), are suggested to be efficient ecological indicators for bird species diversity (Menon & Shahabuddin, 2021 ; Mikusiński et al, 2001 ).…”

“…Additionally, identifying individuals to species level is mainly easy due to the variation of plumage color (Eck & Martens, 2006 ; del Hoyo et al, 2007 ), body size (Alatalo & Moreno, 1987 ; Eck & Martens, 2006 ; del Hoyo et al, 2007 ), and crestedness among species (Eck & Martens, 2006 ; del Hoyo et al, 2007 ). Overall, the ecology of titmice makes them potentially a more efficient indicator group for forest bird abundance than, for example, woodpeckers or cuckoos, which are less abundant and diverse and consist of mainly specialist species (Menon & Shahabuddin, 2021 ; Mikusiński et al, 2001 ; Møller et al, 2017 ).…”