Výsledky projektu Strnadí nářečí a občanská věda: od globální invaze po individuální teritoria

Records of birds introduced into New Zealand in the 19th and 20th centuries for the purposes of acclimatization underpin several of the analyses that show propagule pressure (sensu Lockwood et al. 2005) is a key driver of the establishment success of alien populations (reviewed in Blackburn et al. 2009a, 2009b). Recently, however, the accuracy of the data used in these analyses has been called into question. In particular, two articles published in Notornis claimed to provide evidence of new and previously unreported records of bird introductions from Europe to New Zealand (Santos 2012; Moulton et al. 2014). These records have already been cited several times as evidence of the unreliability of previous studies of the effect of propagule pressure(Santos et al. 2013; Santos & Nakagawa 2013; Moulton & Cropper 2014, 2015). Here, we point out that most of the information presented by Santos (2012) and Moulton et al. (2014) is incorrect, as a result of the data being compiled without using all available historical documents. Our aim is to prevent these new inaccuracies becoming incorporated into further analyses of the establishment success of birds introduced to New Zealand.

The Yellowhammer (Emberiza citrinella) is a bird with a very long history of research in geographic song variation, dating back to the 1920s. Numerous features make the Yellowhammer a suitable model for studying songbird dialects: it is a common and easily recognizable species, has a simple song, keeps singing long into the season, and has dialects (defined by the final song phrase) that are relatively easy to identify. Numerous works have focused on Yellowhammer dialects and their geographic distribution in various parts of Europe, often revealing mosaic-like patterns even at relatively restricted spatial scales. However, it has been repeatedly suggested that Yellowhammer dialects can be divided into two groups showing a macrogeographic pattern of distribution (in some recent works, eastern and western groups of dialects have been mentioned). To evaluate this assumption, data scattered in various published sources need to be pooled. Comparing historical records is nevertheless challenging, as various nomenclatures for Yellowhammer dialects were used until the mid-1980s (when a detailed system coined by Poul Hansen in Denmark was adopted), and older studies often did not differentiate between dialects recognized at present. To facilitate further work on song variation of this species, we summarized published information on the distribution of Yellowhammer dialects in Europe, added data from recordings publicly available online and in selected sound collections, and unified the different dialect nomenclatures used in the past. We demonstrate that the continentalwide distribution patterns of Yellowhammer dialects do not support the existence of broad, geographically distinct dialect groups (eastern vs. western). Furthermore, some of the presently recognized distinct dialect types seem to be parts of a broader continuum. Based on our conclusions, we discuss potential future avenues for Yellowhammer dialect research.

New Zealand harbours a considerable number of alien plants and animals, and is often used as a model region for studies on factors determining the outcome of introductions. Alien birds have been a particular focus of research attention, especially to understand the effect of propagule pressure, as records exist for the numbers of birds introduced to New Zealand. However, studies have relied on compilations of bird numbers, rather than on primary data. Here, we present a case study of the alien yellowhammer (Emberiza citrinella) introduced from the UK to New Zealand, to demonstrate how recourse to the primary literature highlights significant data gaps and misinterpretations in these compilations. We show that the history of the introduction, establishment and spread of the yellowhammer in New Zealand can be reconstructed with surprising precision, including details of the ships importing yellowhammers, their survival rates on board, the numbers and locations of release, and the development of public perception of the species. We demonstrate that not all birds imported were released, as some died or were re-transported to Australia, and that some birds thought to be introductions were in fact translocations of individuals captured in one region of New Zealand for liberation in another. Our study confirms the potential of precise historical reconstructions that, if done for all species, would address criticisms of historical data in the evidence base for the effect of propagule pressure on establishment success for alien populations.

The Yellowhammer (Emberiza citrinella) is a bird with a very long history of research in geographic song variation, dating back to the 1920s. Numerous features make the Yellowhammer a suitable model for studying songbird dialects: it is a common and easily recognizable species, has a simple song, keeps singing long into the season, and has dialects (defined by the final song phrase) that are relatively easy to identify. Numerous works have focused on Yellowhammer dialects and their geographic distribution in various parts of Europe, often revealing mosaic-like patterns even at relatively restricted spatial scales. However, it has been repeatedly suggested that Yellowhammer dialects can be divided into two groups showing a macrogeographic pattern of distribution (in some recent works, eastern and western groups of dialects have been mentioned). To evaluate this assumption, data scattered in various published sources need to be pooled. Comparing historical records is nevertheless challenging, as various nomenclatures for Yellowhammer dialects were used until the mid-1980s (when a detailed system coined by Poul Hansen in Denmark was adopted), and older studies often did not differentiate between dialects recognized at present. To facilitate further work on song variation of this species, we summarized published information on the distribution of Yellowhammer dialects in Europe, added data from recordings publicly available online and in selected sound collections, and unified the different dialect nomenclatures used in the past. We demonstrate that the continental-
wide distribution patterns of Yellowhammer dialects do not support the existence of broad, geographically distinct dialect groups (eastern vs. western). Furthermore, some of the pres-
ently recognized distinct dialect types seem to be parts of a broader continuum. Based on our conclusions, we discuss potential future avenues for Yellowhammer dialect research.

New Zealand harbours a considerable number of alien plants and animals, and is often used as a model
region for studies on factors determining the outcome of introductions. Alien birds have been a particular
focus of research attention, especially to understand the effect of propagule pressure, as records exist for
the numbers of birds introduced to New Zealand. However, studies have relied on compilations of bird
numbers, rather than on primary data. Here, we present a case study of the alien yellowhammer (Emberiza
citrinella) introduced from the UK to New Zealand, to demonstrate how recourse to the primary literature
highlights significant data gaps and misinterpretations in these compilations. We show that the history of
the introduction, establishment and spread of the yellowhammer in New Zealand can be reconstructed
with surprising precision, including details of the ships importing yellowhammers, their survival rates on
board, the numbers and locations of release, and the development of public perception of the species. We
demonstrate that not all birds imported were released, as some died or were re-transported to Australia,
and that some birds thought to be introductions were in fact translocations of individuals captured in one
region of New Zealand for liberation in another. Our study confirms the potential of precise historical
reconstructions that, if done for all species, would address criticisms of historical data in the evidence base
for the effect of propagule pressure on establishment success for alien populations.