Morbidity and Mortality of Mississippi Kites (Ictinia mississippiensis) Presenting to the Wildlife Hospital of Louisiana, USA

Birds of prey, also known as raptors, frequently succumb to anthropogenic causes of morbidity and mortality (MM). This can be through vehicular trauma, ballistic trauma, high-voltage power lines, and wind turbines (Richards et al. 2005; Lucas et al. 2008; Desmarchelier et al. 2010; Kagan 2016), as well as nonpoint sources of MM including DDT and organophosphate toxicoses (Henny et al. 1987). Epidemics of nonanthropogenic etiologies, such as West Nile virus infection, are also well documented among raptors (Ip et al. 2014; Smith et al. 2018).

Many of these raptors are presented to wildlife hospitals. As a result, there have been a number of published articles detailing the MM of raptors, either as species-specific studies or single center experiences with all raptors. Charismatic species such as Bald Eagles (Haliaeetus leucocephalus) and Peregrine Falcons (Falco peregrinus) have been the subject of much work (Harris and Sleeman 2007; Sweeney et al. 2014), but there is a lack of descriptive information on small raptors (<1 kg) such as Mississippi Kites (Ictinia mississippiensis).

Mississippi Kites are small, migratory birds of prey native to North and South America. They are primarily aerial insectivores, with agricultural pest grasshoppers comprising a significant portion of their diets (Parker 2020). A highly adaptable species, Mississippi Kites inhabit a range of habitats from undeveloped lands to increasingly urban environments. This has led to range expansion, and the species' penchant for dive-bombing humans near nests has resulted in increased human-animal contact and conflict (Peterson and Brown 1985; Parker 2020).

From 2014 through 2020, the Wildlife Hospital of Louisiana at Louisiana State University had more than 12,000 admissions across dozens of taxa. Of these, 282 were Mississippi Kites. The primary aim of our study was to describe the primary diagnosis categories and outcomes in this population of Mississippi Kites.

Case data were collected from the online electronic medical record system (Wildlife Rehabilitation MD, Middletown, California, USA) used by the Wildlife Hospital of Louisiana. These data were used to determine a primary diagnosis category—trauma, orphan, neurologic disease, respiratory disease, developmental disease, or unknown for each bird. Our principal study outcomes consisted of raptor release, transfer to a wildlife rehabilitator for continued care or placement as an educational bird, euthanasia during the first 24 h or thereafter of hospitalization, or death within or after 24 h of hospitalization.

Birds in the trauma category were further categorized. Those with radiographic evidence of metal opacities external to the gastrointestinal tract, entry or exit wounds, or at least one identified puncture wound combined with a fracture were considered to have evidence of ballistic trauma. The frequencies of occurrence of compound or open fractures and musculoskeletal injury sites were also examined. For each proportion, 95% binomial confidence intervals (CI) were calculated to estimate the bounds of the true prevalence of each condition in the entire population of Mississippi Kites presenting to wildlife hospitals.

During the 7-yr period, there were 282 Mississippi Kite admissions. A diagnosis category could be determined for 169 (60%) of these (Table 1). Kites were most commonly presented for trauma (115/282, 41%; CI, 35–47%). The second most common reason for presentation was orphaning (44/282, 16%; CI, 12–20%). Developmental (2/282, 1%; CI, 0–3%), neurologic (6/282, 2%; CI, 1–5%), and respiratory (2/282, 1%; CI, 0–3%) disease were the least common reasons for being presented. Neurologically affected kites included those with torticollis, abnormal mentation, or unexplained paraparesis. Suspected causes of neurologic disease included trauma and infectious disease. One kite with respiratory disease was suspected to have, and was treated for, aspergillosis. Of those with developmental disease, one had bilateral angular limb deformities of the legs, while the other had a valgus rotational deformity of the carpometacarpus similar to the “angel wing” condition seen in waterfowl. Of the kites that presented to the hospital alive, there was an overall euthanasia rate of 50% (140/ 282), a mortality rate of 8% (21/282), and a survival (release/transfer) rate of 42% (118/ 282). This survival rate increased to 75% after excluding birds that died or were euthanized within 24 h of hospitalization.

Among those with a known diagnosis, a high degree of suspicion or physical evidence of ballistic trauma was present in 7% (11/169) of the kites. Of these 11, three had at least one fractured bone. We were unable to determine rates of other potential trauma categories such as vehicular trauma. Kites presented with trauma were significantly more likely to have one or more skeletal fractures or luxations (85/ 115, 74%; CI, 65–82%) than to not have this type of lesion (30/115, 26%; CI, 18–35%; Fig. 1). Mississippi Kites were more likely to present with wing fractures (71/95, 75%; CI, 65–83%) than leg fractures (13/95, 14%; CI, 7–22%); humeral (23/95, 24%; CI, 16–34%) and radial and/or ulnar (19/95, 20%; CI, 12–29%) fractures were the most common fractures identified (Fig. 1). Thirty-nine (45%) of these birds were noted to have open fractures, although this may be an underestimate as no formal protocols were in place with guidance on how to record fracture classifications.

Similar to reports for other species, trauma was the single most important contributor to the MM of Mississippi Kites presenting to this wildlife hospital (Deem et al. 1998; Wendell et al. 2002; Harris and Sleeman 2007; Hernandez 2018). Our study kite population had comparable rates of ballistic trauma (11/282, 4%)—defined as number of ballistic trauma cases/ total cases—to those observed in small diurnal raptors presenting to a wildlife hospital in Virginia (26/669, 4%; Richards et al. 2005). While these birds likely only represent a small proportion of the wild Mississippi Kites that are shot, these data are useful for understanding future trends of raptor persecution in Louisiana and elsewhere.

Resource limitations generally made determination of an etiologic diagnosis for animals with neurologic or respiratory disease unfeasible. Despite these and other concerns, this is the first report of reasons for admission and outcomes of Mississippi Kites presenting to a wildlife hospital. Such reports are important as baseline assessments that may allow researchers to identify changing MM trends in birds presenting to wildlife hospitals and, in turn, wild populations.

This work was supported by the National Center for Advancing Translational Sciences, National Institutes of Health, award TL1TR002546. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.