Ecology of Canada geese in urban area of Iowa
April 2018 - September 2021
- Iowa Department of Natural Resources
STUDY NEED: Temperate breeding Canada geese (Branta canadensis maximus) were extirpated from Iowa in the early twentieth century until the Iowa Conservation Commission initiated a reintroduction program in 1964 (Bishop and Howing 1972). Iowa’s Canada goose population has gone from near zero to April population estimates that occasionally exceed 100,000 (Jones and Hancock 2014). At the same time Iowans perception of Canada geese has evolved from an uncommon and charismatic bird to a widespread species that is occasionally viewed as a nuisance. In recent years the estimated harvest of Canada geese in Iowa has exceeded that of mallards, an indication of the resilience and significance of this population (Raftovich et al 2017). It is critical that our monitoring and management keep pace with the changes this population is experiencing. An unexpected behavior of Canada geese post-reintroduction has been their exploitation of urban and suburban environments (urban and suburban environments will be defined as those within municipal city limits, hereafter referred to as “urban areas”). Canada geese were initially re-introduced in rural marshes and were thought of as a wary bird requiring abundant wetland habitat, specifically cattail marshes. However, Canada geese have successfully exploited urban areas in Iowa and throughout North America (Balkom 2010 and Beston et al. 2014). Conflicts with Canada geese traditionally occurred in rural areas, specifically on emerging agricultural crops. Beginning in 2012 this pattern reversed and the majority of nuisance complaints regarding Canada geese now occur in urban areas (Bunger 2016). The abundance of Canada geese in urban areas is resulting in novel problems that traditional management actions may not adequately address. The primary management action to control Canada goose populations has traditionally been recreational harvest (Iverson 2013). However, hunting is often limited in urban areas due to safety concerns and local ordinances. This may provide an opportunity for rapid population growth while at the same time geese become acclimated to humans due to their close proximity and artificial feeding by well-meaning citizens. This can result in a large goose population within city limits which may attract migrating geese thereby exacerbating the perceived size of the goose population. In these situations conflicts such as aggressive behavior by geese, fecal deposition, property damage, and vehicle collisions increase. Actions to mitigate conflicts can be controversial with varied opinions amongst stakeholders. In order to adequately develop management actions wildlife agencies require information on the ecology of Canada geese in urban areas. This information is generally lacking as the majority of research on Canada geese has occurred in rural areas. STUDY OBJECTIVES: Objective 1. Evaluate the movement of Canada geese captured in urban areas. Compare to the movement of geese captured in rural locations where the goose hunting season is closed. Determine the susceptibility of Canada geese captured in urban areas to hunting during the Special September Canada Goose season and the conventional Canada goose hunting season. Objective 2. Estimate annual harvest and survival rates for Canada geese captured in urban areas. Evaluate a three age-class model to estimate harvest and survival rates of Canada geese in Iowa. Where possible incorporate both live recaptures and dead recoveries to improve statistical precision and accuracy. STUDY EXPECTED RESULTS OR BENEFITS: The primary benefit of this research will be an increased understanding of Canada geese in urban areas of Iowa. This will allow the Iowa DNR to develop management actions that will mitigate conflict caused by Canada geese in this novel environment. The DNR is striving to find a balance between managing a valuable wildlife resource and mitigating conflict. The results of this project will allow for an update and re-evaluation of Iowa DNR’s Canada Goose Management Plan (Jones and Hancock 2014). This project closely aligns with the first strategic goal identified in the Wildlife Research Section’s Strategic Plan “Iowa will have viable wildlife populations that are compatible with modern landscapes” (Iowa DNR 2016). Results will also be applicable to other states and provinces of the Mississippi Flyway, many of which are experiencing similar conflicts. Specifically, the results of this project will answer questions regarding the movement of Canada geese in urban environments such as: Do geese captured in urban areas ever leave urban areas? Is there seasonal variation in the movement of urban geese? This project will also answer questions regarding the population dynamics of urban geese, such as a comparison of harvest and survival rates of urban geese and the statewide population. Finally, this project will assess whether recreational harvest is an adequate tool to control urban populations or whether other, more direct management actions are warranted. The Iowa DNR currently allocates 9 of the 107 days available to hunt Canada geese to 3 zones surrounding urban areas during a Special September Canada Goose season. This season is intended to target nuisance geese in urban areas. However, the harvest and impact of this season on the population dynamics of geese in urban areas is unknown. The results of this project will allow the Iowa DNR to evaluate this season as a management tool to control Canada geese in urban areas.