Horned lark, strigata subspecies COSEWIC assessment and status report: chapter 7
Population Sizes and Trends
The Canadian population of Eremophila alpestris strigata has declined to the verge of extirpation. Historically, the population was likely very small and locally distributed. Suitable habitat would have been limited to sand dunes and very sparsely vegetated natural grasslands prior to the arrival of European settlers. Subsequent to European arrival, additional habitat would have been created through clearing forest and draining wetlands. Eremophila alpestris strigata was first documented both in the lower Fraser River valley and on southern Vancouver Island in the late 1880s.
In the lower Fraser River valley, the population is described as “small” and is said to have “persisted from the 1920s through the next few decades” although precise population estimates are not made (Campbell et al. 1997). By the 1960s, breeding populations were confined to the mowed fields at the Vancouver International Airport, possibly near Abbotsford (Campbell et al. 1997), and in sand dune habitat on Sea and Iona islands (JMC unpublished data). As many as 7 birds were noted on Sea Island between 1963 and 1966. The last confirmed breeding record on Sea Island was in 1978, although breeding was suspected in 1981 (Butler and Campbell 1987). Although Weber et al. (1990) list the Horned Lark, strigata subspecies as a rare resident at Sea Island, the last known summer occurrence was 10 seen on 1 May 1987 (Campbell et al. 1997, W.C. Weber, pers. comm.). These birds were not identified to subspecies so they may not have been E. a. strigata, although lark migration is usually completed by the end of April (Campbell et al. 1997).
Although there are no breeding records from Vancouver Island or the Gulf Islands (Campbell et al. 1997), based on specimen records, it seems possible that Eremophila alpestris strigata formerly bred in the region. At least nine Eremophila alpestris strigata specimens were collected on Vancouver Island, between 1890 and 1953 (Appendix 1). Unfortunately, the amount of collection or nest finding effort was not documented, but it is speculated that effort was not extensive and this cryptic bird could have been easily overlooked. Therefore, given that there are some specimens, it is assumed that Eremophila alpestris strigata was not rare.
Campbell et al. (1997) considered Eremophila alpestris strigata to be extremely scarce in the lower Fraser River valley and Fraser et al. (1999) considered it extirpated on southeastern Vancouver Island, although systematic surveys have never been undertaken in either region. However, in 2002, while searching southern Vancouver Island for Vesper Sparrows, a species with similar habitat requirements, a single male was observed in 30 survey days (approximately 240 hrs; Beauchesne 2002). This bird was engaged in a breeding display; however, a mate was not located, nor was a nest found in approximately 16 hours of search time (SMB unpublished data). In 2003, 30 days (approximately 240 hrs) were again spent searching in similar habitat types, but no Horned Larks were located (Beauchesne in prep.). No other recent records of this subspecies are known to exist (D. Allinson pers. comm.; N. Dawe pers. comm.; M. McNichol pers. comm.; G. Monty pers. comm.).
Population levels of Horned Lark, strigata subspecies were not addressed by Beason (1995), even though it was widely believed that numbers were declining. In Washington and Oregon, there are only an estimated 300-500 birds remaining (S. Pearson, pers. comm.), of which approximately 100 occur in the Puget Sound lowlands of Washington with the remainder on coastal Washington and on islands in the Columbia River. Many historically occupied territories in Washington and Oregon are now vacant (S. Pearson pers. comm.).
In the San Juan Islands of Washington (approximately 18 km across the Strait of Juan de Fuca, east of southeastern Vancouver Island), Horned Larks were first noted as breeding in 1946, after which they were recorded as breeding “commonly at times”. Breeding has not been recorded since 1962 (Rogers 2000).
In western Oregon, the Horned Lark, strigata subspecies was noted as a common breeder in the 1930s. It was even “particularly abundant” in Polk and Yamhill Counties. In the fall groups of dozens or hundreds were noted (Gabrielson and Jewett 1940). However, possible confusion between subspecies raises question as to the veracity of that account and the possibility that they never were that common in Oregon (Rogers 2000).
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