Blood Parasites in Owls with Conservation Implications for the Spotted Owl (Strix occidentalis)

Abstract

The three subspecies of Spotted Owl (Northern, Strix occidentalis caurina; California, S. o. occidentalis; and Mexican, S. o. lucida) are all threatened by habitat loss and range expansion of the Barred Owl (S. varia). An unaddressed threat is whether Barred Owls could be a source of novel strains of disease such as avian malaria (Plasmodium spp.) or other blood parasites potentially harmful for Spotted Owls. Although Barred Owls commonly harbor Plasmodium infections, these parasites have not been documented in the Spotted Owl. We screened 111 Spotted Owls, 44 Barred Owls, and 387 owls of nine other species for haemosporidian parasites (Leucocytozoon, Plasmodium, and Haemoproteus spp.). California Spotted Owls had the greatest number of simultaneous multi-species infections (44%). Additionally, sequencing results revealed that the Northern and California Spotted Owl subspecies together had the highest number of Leucocytozoon parasite lineages (n = 17) and unique lineages (n = 12). This high level of sequence diversity is significant because only one Leucocytozoon species (L. danilewskyi) has been accepted as valid among all owls, suggesting that L. danilewskyi is a cryptic species. Furthermore, a Plasmodium parasite was documented in a Northern Spotted Owl for the first time. West Coast Barred Owls had a lower prevalence of infection (15%) when compared to sympatric Spotted Owls (S. o. caurina 52%, S. o. occidentalis 79%) and Barred Owls from the historic range (61%). Consequently, Barred Owls on the West Coast may have a competitive advantage over the potentially immune compromised Spotted Owls.

Health of an ex situ population of raptors (Falconiformes and Strigiformes) in Mexico: diagnosis of internal parasites

“…and Trypanosoma avium are the hematozoa recorded in birds of prey worldwide (Deem 1999, Muñoz et al 1999, Remple 2004, Ishak et al 2008, Krone et al 2008, Leppert et al 2008. Nevertheless, this is a first record of Haemoproteus spp.…”

“…The process of host-parasite cointroduction, termed "pathogen pollution" (Cunningham 1996, Daszak et al 2000, may have a heightened ecological impact by conferring competitive advantage to the invading host, a phenomenon known as "apparent competition" or "parasite-mediated competition (Cunningham et al 2003). In United States, three subspecies of Spotted owl (Strix occidentalis caurina, S. o. occidentalis and S. o. lucida) are threatened by habitat loss and the range expansion of the Barred owl (S. varia) (which is also a source of novel pathogens, such as blood parasites), potentially harmful for threatened Spotted owls (Ishak et al 2008). Pathogen pollution may have significant implications for animal welfare, endangering the conservation status of wildlife due to biodiversity loss (Daszak et al 2000, Cunningham et al 2003.…”

Untested assumptions about within-species sample size and missing data in interspecific studies

“…We also obtained data from multiple sources that screened blood of captured adult birds of any sex that breed in Europe for haemoparasite prevalence (Bennett et al 1982;Haberkorn 1984;Merino et al 1997;Valkiūnas et al 1999;Krone et al 2001;Shurulinkov and Golemansky 2003;Mendes et al 2005;Palinauskas et al 2005;Wiersch et al 2007;Ishak et al 2008;Krone et al 2008;). This compiled dataset included 150 bird species that had at least one individual sampled, while the maximum within-species sample size was 370 (CV 0 176.8 %).…”

Local parasite lineage sharing in temperate grassland birds provides clues about potential origins of Galapagos avian Plasmodium

“…2003) and the other from a barred owl ( Strix varia ), also sampled in California (Ishak et al. 2008). This suggests that if migrating bobolinks did introduce this lineage to the Galapagos Islands, they most likely acquired this parasite in their North American breeding grounds.…”

“…This lineage was detected in other North American birds that either have a distribution that extends into South America (Great Horned Owl, Bubo virginianus ; Ishak et al. 2008) or in common yellowthroats (Pagenkopp et al. 2008), for which the overwintering range includes the northern part of South America.…”