Woodland birds are bird species which depend on native woodlands. They are sometimes called woodland-dependent birds. Unfortunately, woodlands have been widely cleared for agriculture and urban development leading to a widespread belief that woodland birds must be declining. Many have studied the decline of woodland birds, most commonly studying the effect of changing tree cover and fragmentation.
The results of these studies vary. Some find evidence of decline; others dispute that a decline is taking place. Similarly, the nature of the relationship between woodland birds and tree cover and fragmentation varies substantially too. These differences might be due to regional or scale differences between studies. But could there also be underlying disagreement about what actually constitutes a 'woodland bird'?
A shared understanding of the meaning of words is central to communicating ideas in all disciplines. In ecology, there have been sporadic efforts to promote consistency in terminology but little progress. Inconsistent terminology can lead to a range of problems including difficulties in finding relevant studies, redundant investigations and an inability to synthesise across studies (eg, meta-analysis). It can also create problems when communicating findings to other scientists, policy makers and the public. On the other hand, some argue that consistent terminology is unnecessary because often the meaning is clear from its context.
So, how important is consistent terminology when it comes to determining the conservation status and trends of a group of birds loosely referred to as 'woodland birds'? Hannah Fraser and colleagues at the University of Melbourne set out to answer this question. They systematically reviewed the literature and compiled a set of 38 lists of woodland birds. This allowed us to work out how consistently each species was classified as a woodland bird.
They found that 8 species were always classified as woodland birds and 13 species were always classified as non-woodland birds. The remaining 144 species were sometimes classified as woodland birds and sometimes as non-woodland birds.
This surprisingly high inconsistency has a significant impact on research involving woodland birds.
"When comparing results from studies using different classifications it is impossible to know whether differences are attributable to data collection, survey area or analyses or whether they are due to differences in classification," says Hannah Fraser. "This essentially renders all studies with non-identical lists incomparable.
"If we could standardise our approach to woodland birds we believe that there may be scope to list a woodland-bird Threatened Ecological Community under the EPBC Act. The first step towards this is identifying which species comprise a woodland bird community; then we will need to determine whether the community qualifies as threatened."
Long story short, how we name woodland birds, indeed any bird group, is important. It's about time the conservation science fraternity acknowledged this and we move to some accepted standard within which we can reliably pool our common knowledge.
Image: The brush cuckoo is classified a woodland bird in 62.5% of lists. (Photo by Eric Vanderuys)