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ORNITOLOGIA NEOTROPICAL 15 (Suppl.): 301–307, 2004 © The Neotropical Ornithological Society

TINAMOUS AND AGRICULTURE: LESSONS LEARNED FROM THE

Jeffrey J. Thompson

Daniel B. Warnell School of Forest Resources, University of Georgia, Athens, Georgia 30602-2152, USA. E-mail: [email protected]

Resumen. – Tinámidos y agricultura: lecciones aprendidas de los Galliformes. – El 32% de las 47 especies del orden Tinamiformes viven en pastizales. Estas especies están distribuidas en las regiones tro- picales y templadas, pero la mayoría se encuentran en las regiones australes de América del Sur. Las pobla- ciones de estas especies son susceptibles a la conversión de la tierra para agricultura y la intensificación del uso de la tierra después de la conversión. Existe poca información sobre los efectos de la conversión y uso de la tierra en las poblaciones de tinamúes, pero hay mucha investigación sobre sus efectos en los Galliformes. Al considerar los tinamúes que viven en pastizales como los equivalentes ecológicos de los Galliformes, se pueden hacer inferencias generales sobre los posibles efectos de la conversión y inten- sificación del uso de la tierra en estas especies. Es más eficiente ver los impactos potenciales del uso de la tierra como una función de la interacción de múltiples gradientes: el área de la vegetación natural, la estructura de la vegetación, la intensidad de la agricultura y ganadería, y el uso de herbicidas y pesticidas. Este modelo permite una cuantificación de la conveniencia de un lugar para cada especie, flexibilidad potencial de las especies a los cambios de hábitat, la comparación entre lugares y funciona como una herramienta para determinar rápidamente el valor de conservación de los lugares en el paisaje. Abstract. – inhabiting and steppes represent 32% of the 47 species of the Tinami- formes. These species are both tropical and temperate in their distribution but the majority is confined to austral . Populations of these species are susceptible to land conversion for agriculture, as well as intensification of land use after conversion. Although little information exists on the effects of land conversion and use on populations, there is an extensive amount of research on these effects on gallinaceous . By viewing the grassland and steppe dwelling as ecological equivalents to the Galliformes, general inferences can be made about the projected impacts of land conversion and the inten- sity of use on these species. It is most efficient to view the potential impacts of land use as a function of the interaction of several gradients: area of natural vegetation, vegetation structure, intensity of cropping and grazing, and herbicide and pesticide use. This model allows for a quantification of site suitability by species, potential resilience of species, comparison among sites, and serves as a tool to rapidly assess the conservation value of sites within the landscape. Accepted 29 December 2003. Key words: Tinamiformes, Galliformes, agriculture, grazing, agro-ecosystems, , gamebirds.

INTRODUCTION grazing and row crops (from here on agricul- ture) (White et al. 2000). Consequently, much Temperate and tropical grassland of the from these natural ecosys- (grasslands, steppes, ) have been, and tems is now associated with a landscape continue to be, extensively converted for matrix of varying complexity, consisting of

301 THOMPSON natural and man modified habitats. Increas- resent 32% of the 47 species and, in most of ingly, these agro-ecosystems have become less South America, occupy the majority of niches diversified in content and complexity in grassland habitats associated with the galli- (McNeely et al. 1995). forms in other regions (Davies 2002, del During the post-World War II era, grass- Hoyo 1992 et al.). Despite their diversity and land conversion and/or agricultural intensifi- importance in sport, commercial, and subsis- cation have increased in intensity and extent tence harvest, little research has focused on (Fuller 2000). Although and North these birds. Furthermore, as in the rest of the America have been placed under high-input world, the grassland habitats that these birds agriculture over the last half-century, other occupy have been, and continue to be, under areas such as South and intensive agricultural pressure. For example, have lagged behind until recently (Pero & the pampas of Argentina and Uruguay have Crowe 1996, Viglizzo & Roberto 1998). This been nearly completely converted to row process of land conversion and agricultural crops and grazing over the last 150 (Hall intensification has been attributed to the glo- et al. 1992), and for the past decade have been bal declines of grassland and shrubland birds subjected to rapidly increasing intensification (Aebischer et al. 1999, Vickery & Herkert (Viglizzo & Roberto 1998). 1999, Murphy 2003, Peterjohn 2003). Despite this continuing land conversion, Among the grassland dependent birds, the and increasingly intense utilization, there is a population declines of the gallinaceous - conspicuous lack of research into their effects birds were some of the first to draw the atten- on biodiversity in grassland ecosystems within tion of researchers and the public. The first, South America. For tinamous however, it is and one of the most thorough studies into the possible to make inferences based upon the effects of farmland composition and manage- extensive body of research into the impacts of ment on galliform populations was on the land conversion and agriculture on galliforms. declines of the Grey (Perdix perdix) Here I draw from examples on the effects of in England (Potts 1980, 1986). This research agricultural land conversion and intensifica- highlighted the importance of the composi- tion on grassland species in general, and tion and configuration of the agricultural galliforms in particular, highlighting the major landscape and how it is managed, particularly environmental gradients that impact these the use of herbicides and pesticides. These birds, for the purpose of assessing the quality have become major themes in the research of of grasslands and their associated agro-eco- grassland birds (Vickery & Herkert 1999, systems for tinamous, as well as to direct Aebischer et al. 2000, Murphy 2003, Peterjohn future research. 2003) and have been key topics of research for many gamebirds (Rands et al. 1988), CASES IN THE GALLIFORMES including Northern Bobwhite ( virgi- nianus; Brennan 1999), prairie chickens (Tym- Due to their importance as gamebirds, the panuchus spp.; Fuhlendorf et al. 2002, Geisen Galliformes are a well-studied order and sub- 1998, Ryan et al. 1998), Helmeted sequently population dynamics are well docu- (Numida meleagris; Pero & Crowe 1996, Malan mented for many species (e.g., Fuller et al. & Benn 1999, Ratcliffe & Crowe 2001) and 2000). Over the last half-century however, as francolins (Francolinus spp.; Little & Crowe with many grassland species, galliforms asso- 1998; Jansen et al. 1999, 2000). ciated with grasslands and agro-ecosystems Grassland tinamous (Tinamiformes) rep- have exhibited significant population declines

302 TINAMOUS AND AGRICULTURE across several continents. Important examples has led to the management of pastures for are the Northern Bobwhite (Brennan 1999) silage rather than for hay. The increase in and prairie chickens (Johnsgard 1983, Hous- management for silage allows for higher ton 2002) in , the Helmeted stocking levels of livestock since forage can be Guineafowl (Pero & Crowe 1996, Malan & subsidized with high quality fodder. High live- Benn 1999, Ratcliffe & Crowe 2001) and the stock densities have been contributing to francolins (Little et al. 1995; Jansen et al. 1999, decreases in populations of several galliform 2000) in , and the Gray Partridge species (Jansen et al. 1999, Robbins et al. in Europe (Potts 1980, 1986). 2002). Furthermore, mechanization has The decline of populations of these spe- allowed for more frequent cutting of these cies is mostly attributed to changes in the pastures for silage, leading to increased loss of extent, intensity, and type of land use. Inter- nests and young. estingly, several of these species initially The use of petrochemicals, associated increased their ranges and/or populations as a with the decrease in landscape complexity and function of anthropogenic changes to the diversity, had major implications for popula- landscape. These changes, however, eventu- tions of birds in agro-ecosystems due to ally passed a threshold where populations impacts on brood survival (Palmer 1995, began to decline. The key to making infer- Fuller 2000). In particular, the indirect effects ences to the tinamous and applying them for of herbicides and the direct effects of insecti- research and management is to understand cides greatly decrease the quality of agricul- the major factors associated with land use that tural land as brood , and subsequently have both positively and negatively impacted brood survival (sensu Potts 1986). Further- galliform populations in grasslands and agro- more, the use of fertilizers on silage pastures ecosystems (Johnsgard & Wood 1968, Johns- leads to a decrease in floral diversity and gard 1983, Johnson & Knue 1989, Pero & structure, and is associated with a decrease in Crowe 1996, Brennan 1999, Malan & Benn invertebrate diversity (Fuller 2000). 1999, Ratcliffe & Crowe 2001, Houston 2002). ASSESSING THE AGRICULTURAL IMPACTS AGRICULTURAL CHANGES The aforementioned factors interact synergis- As discussed by Fuller (2000), the intensifica- tically to decrease the complexity and the tion in agriculture that has occurred has been diversity of the landscape and the quality of largely due to increased mechanization, the habitats within the landscape. Although the use of chemical fertilizers, pesticides and her- degree to which each factor interacts to affect bicides, and decreased diversity of crop types. a species is species dependent, these factors Mechanization allows for the cultivation of can be generalized into several principal gradi- more area and larger fields, the large-scale ents, each consisting of several components. application of fertilizers, pesticides and herbi- These gradients are: 1) pesticide and herbicide cides, and more frequent tilling or cutting of use, 2) vegetation structure, 3), intensity of hedgerows and field borders. land use, and 4) area of natural vegetation (i.e., The use of fertilizers eliminates the need not being managed for row crops or silage). to leave fields fallow or in pasture, eliminates Pesticide and herbicide use includes chem- the need for manure, thus eliminating the ical strength, amount applied, and frequency need for and associated pastures, and of application. Vegetation structure includes

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FIG. 1. Graphical model of the effects of increasing agricultural intensification on grassland Galliformes. This may also serve as a model for grassland tinamous in South America. measures of height, density, and species diver- tant since agro-ecosystems are dynamic envi- sity. Intensity of land use is represented by ronments, and subsequently need to be field size, crop diversity, crop rotation, and assessed and measured at regular intervals livestock densities and grazing rotations. Area throughout the . of natural vegetation not only includes graz- These gradients act synergistically to ing and fallow land, but vegetation and crop impact populations, but it can be hypothe- stubble within row crops. The intensity of sized that there are two general responses that land use and area of natural vegetation can be expected based upon the aforemen- together represent a measure of landscape tioned examples, with the magnitude of the composition that has been illustrated to be response dependent upon the species (Fig. 1). important for many galliforms (Potts 1986, The first is where populations initially Aebischer & Potts 1998, Malan & Benn 1999, increase as a function of cultivation and/or Niemuth 2000). grazing, when not intensive or extensive; It is necessary to realize that the impor- however, populations begin to decline rapidly tance that each of these gradients has for a after the combined effects of the gradients species will not only depend upon the species pass a certain magnitude (Fig. 1a). Such popu- but upon the temporal needs of individuals lation responses have been documented for and, subsequently, dietary and habitat require- Helmeted (Pero & Crowe 1996) ments need to be assessed for all stages of a and Greater Prairie-Chickens (Tympanuchus species life cycle. This is particularly impor- cupido; Johnsgard & Woods 1968, Johnsgard

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1983, Johnson & Knue, 1989, Houston 2002). these systems. As pointed out by Jansen et al. The second response is where populations (1999), gallinaceous gamebirds can serve as remain stable despite initial land conversion excellent indicators of ecosystem health. and management but, as in the first example, Given that tinamous serve as ecological decline after the combined impacts of the gra- equivalents to the galliforms, research into the dients reach a certain threshold (Fig. 1b). This effects of land use will not only serve to con- response has been evident with the popula- serve and guide management of these species, tion declines of the Northern Bobwhite in the but will contribute to conservation of the United States, associated with land conversion increasingly threatened biodiversity associated in the 19th and early 20th centuries (Brennan with South American grasslands and agro- 1999), and with the Redwing Francolin (Fran- ecosystems. colinus levaillantii) stemming from over grazing (Jansen et al. 1999). ACKNOWLEDGMENTS

RESEARCH DIRECTIONS This presentation and the organization and attendance of the symposium “Ecology and To successfully apply this model to the con- Conservation Status of the Tinamiformes” at servation and management of tinamous in the VII Neotropical Ornithological Con- agricultural landscapes there needs to be gress, Termas de Puyehue, was partially quantitatively rigorous population estimation made possible through funding from the of species along various intensities of each of American and Waterfowl Society the proposed gradients (sensu Conroy & Car- and the Graduate School of the University of roll 2001). This will allow for an assessment Georgia. This manuscript was improved by of the impacts of different land use regimes comments from John P. Carroll. on populations and provide baseline data to assess long term population trends. REFERENCES Such research only yields the effects of land use; however, and given the small Aebischer, N. J., & G. R. Potts. 1998. Spatial amount of information on tinamou biology, changes in Grey Partridge (Perdix perdix) distri- research needs to concentrate on understand- bution in relation to 25 years of changing agri- ing the mechanisms that drive population culture in Sussex, U.K. Gibier Faune Sauvage, dynamics by researching the basic biology of 15: 293–308. each species throughout the year. Moreover, if Aebischer, N. J., A. D. Evans, P. V. Grice, & J. A. the model of Galliformes as an inference Vickery. 2000. Ecology and conservation of holds true, there should be an emphasis on lowland farmland birds. British Ornithologistsí understanding the reproductive biology and Union, Hertfordshire, UK. the factors that affect chick survival, since Brennan, L. A. 1999. Northern Bobwhite (Colinus these appear to be key factors in determining virginianus) In Poole, A., & F. Gill (eds). The birds of North America, No. 397. The Birds of population size (Potts 1980, 1986, Palmer North America, Inc., Philadelphia, Pennsylva- 1995). nia. Given the rapid and continued conversion Conroy, M. J., & J. P. Carroll. 2001. Estimating of grassland systems to agriculture through- abundance of Galliformes: Tools and applica- out South America and the intensification of tion. Pp. 204–215 in Woodburn M., P. that agriculture, there looms a growing crisis McGowan, J. Carroll, A Masavi, & D. Z. Zang for the conservation of biodiversity within (eds.). Galliformes 2000: Proceedings of the 7th

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