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Terrestrial Birds in the Lower Coos Watershed

    Summary:

  • Since 1980, some terrestrial bird species have become more abundant while others have declined. However, most birds show no clear trend, suggesting that local bird populations are generally stable.


  • Neotropical migrants may be overwintering in the Coos system more frequently, a trend that could be correlated with changing climate.


  • Conservation efforts appear to have enhanced local populations for some key bird species (e.g., ospreys and bald eagles).


  • Some highly adaptable, “synathropic” species such as crows, ravens, pigeons, and doves may benefit from habitat created by human development


Figure 1. Terrestrial bird survey sites in and near the project area. Data: Rodenkirk n.d., USGS 2014

Figure 1. Terrestrial bird survey sites in and near the project area. Data: Rodenkirk n.d., USGS 2014

What’s Happening?

Raptors

This section summarizes the status and trends of raptor populations, including hawks, eagles, and other birds of prey. Regional data are presented at a statewide level using breeding population estimates as a proxy for abundance. A discussion of Coos estuary data, which use Audubon Christmas Bird Count (CBC) sightings to project trends in local raptor abundance, follows (Figure 1). The Local Raptor Trends section describes the status of raptor species that display the most apparent abundance trends since the 1980s.

Statewide Raptor Trends

The United States Geological Survey (USGS) Patuxent (MD) Wildlife Research Center (2014) conducts the North American Breeding Bird Survey (BBS), which includes 144 survey sites in Oregon. One of the Oregon sites is located within the project area and three sites are located near the project area (Figures 1 and 2). This survey is conducted annually along preselected observational “routes.” The BBS data are used here as indices of relative bird species abundance and should not be interpreted as estimates of the total population size (D. Ziolkowski, pers. comm., November 24, 2014).

Figure 3 displays the BBS abundance data for six raptors species that have displayed clear trends (1966-2012) in Oregon. It should be noted that some of these trends are subject to data limitations (e.g., small sample size) that can reduce the reliability of the results. Please see the chapter summary for more information about these limitations.

Local Raptor Trends

Below we focus on raptor species in the Coos estuary that show strong evidence of changing populations:

Figure 3. North American Breeding Bird Survey (BBS) data for statewide abundance trends (1966-2012).The BBS data show six raptor species exhibiting clear trends over time. The American kestrel (Falco sparverius) has shown a statistically significant decline, while the Turkey Vulture (Cathartes aura) , osprey (Pandion haliaetus) , and Red-tailed Hawk (Buteo jamaicensis) have shown significant increases. Data: USGS 2014

Figure 3. North American Breeding Bird Survey (BBS) data for statewide abundance trends (1966-2012).The BBS data show six raptor species exhibiting clear trends over time. The American kestrel (Falco sparverius) has shown a statistically significant decline, while the Turkey Vulture (Cathartes aura) , osprey (Pandion haliaetus) , and Red-tailed Hawk (Buteo jamaicensis) have shown significant increases. Data: USGS 2014

Osprey (Pandion haliaetus)

From 1980-1997, there were no Osprey sightings in the Coos estuary during the CBC (Audubon 2014, Rodenkirk 2012b, Cornu et al. 2012). However, since 1997, Ospreys have been sighted consistently, with 1-3 birds wintering annually (Audubon 2014; Rodenkirk 2012; T. Rodenkirk, pers. comm., January 19, 2012; Cornu et al. 2012, )(Figure 4).

Figure 4. Osprey are commonly found in the Coos estuary during summertime, but CBC data indicate that the wintering population of osprey has increased over time. Photo Credit: B.N. Singh taken from Cornell 2014

Figure 4. Osprey are commonly found in the Coos estuary during summertime, but CBC data indicate that the wintering population of osprey has increased over time. Photo Credit: B.N. Singh taken from Cornell 2014


Figure5. Coos Bay CBC data indicate that local midwinter bald eagle abundance has generally increased since 1980. Some data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012

Figure5. Coos Bay CBC data indicate that local midwinter bald eagle abundance has generally increased since 1980. Some data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012


Figure 6. USGS Patuxent Wildlife Research Center conducts the North American Breeding Bird Survey (BBS) along observational routes at 144 sites in Oregon (white), including one site within the study area (yellow). The project area (cross hatch) has been highlighted for reference. Habitat within proximity to the project area (< 20 miles) is also highlighted (see Figure 1 for reference). Data: USGS 2014








Bald Eagle (Haliaeetus leucocephalus)

Historically, bald eagle populations were in danger of extinction throughout their range, but they have since recovered (USFWS 2013). The CBC data, which show a generally increasing trend of midwinter eagle abundance in the Coos estuary, suggest that the overall recovery of this species may be mirrored by the recovery of local bald eagle populations (Figure 5).

Red-shouldered Hawk (Buteo lineatus)

Red-shouldered hawks were not sighted during the Coos Bay CBC until 1993. Sightings have generally increased since then, averaging nearly 12 sightings annually from 2006-2013 alone (Figure 6).

Other Raptors

Many raptors species are abundant in the Coos estuary, but most of these birds have displayed neither clearly increasing nor clearly decreasing population trends over time. Figure 7 summarizes CBC data for commonly sighted raptors in Coos Bay.

Figure 6. Coos Bay CBC data indicate that local midwinter red-shouldered hawk abundance has generally increased since 1980. Some data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012

Figure 6. Coos Bay CBC data indicate that local midwinter red-shouldered hawk abundance has generally increased since 1980. Some data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012



Figure 7. Common raptor species that display neither clearly increasing nor clearly decreasing population trends in the Coos estuary (1980-2013). Data: Audubon 2014, Rodenkirk 2012; Bird Sketches: Csuti et al. 1997

Figure 7. Common raptor species that display neither clearly increasing nor clearly decreasing population trends in the Coos estuary (1980-2013). Data: Audubon 2014, Rodenkirk 2012; Bird Sketches: Csuti et al. 1997



Owls

This section discusses trends in owl abundance at a statewide level as well as locally. Emphasis is given to species whose populations have displayed clear trends over time.

Thenorthern spotted owl (Strix occidentalis caurina) and the northern barred owl (Strix varia varia) are mentioned here briefly. Trends for these species are discussed in further detail in the Birds of Special Concern data summary.

Statewide Owl Trends

The great horned owl (Bubo virginianus) is the only owl species surveyed by BBS to exhibit a clear trend (Figure 8). It appears great horned owl populations are decreasing, though the trend is not statistically significant.

Research suggests that the northern barred owl and northern spotted owl have exhibited clear trends at a regional level. Since the early 1990s, the barred owl has expanded its range into southwestern Canada, the northern Rockies, and Pacific Northwest, while the spotted owl has declined throughout its range (Courtney et al. 2004, Davis et al. 2011, Zabel et al. 1996, Forsman et al. 2013).

Owls in the Lower Coos Watershed

Few owl species appear to exhibit either clearly increasing or clearly decreasing population trends in the project area. The exceptions are the northern spotted and barred owls. In upland habitats associated with the lower Coos watershed, spotted owl populations have declined while barred owl populations have grown (Figure 9).

Table 1 summarizes local CBC count data for the most commonly observed owl species. In some cases, the CBC owl species data are relatively sparse, because not all owls are observed every year (e.g., northern saw-whet owl, northern pygmy owl). Available data indicate no clear abundance trend for commonly sighted owl species (Figure 10).

Table 1. List of commonly observed owl species in the lower Coos watershed. Abundance index shows the number of years that the species was observed during the CBC (1980-2013). The CBC was not conducted from 1987-1989 and again in 2010. Therefore, if a species is present every year since 1980, the corresponding abundance index is 30. Data: Audubon 2014, Rodenkirk 2012

Table 1. List of commonly observed owl species in the lower Coos watershed. Abundance index shows the number of years that the species was observed during the CBC (1980-2013). The CBC was not conducted from 1987-1989 and again in 2010. Therefore, if a species is present every year since 1980, the corresponding abundance index is 30. Data: Audubon 2014, Rodenkirk 2012



Figure8. Data from the BBS suggest that great horned owl populations statewide have declined over time, although this trend is not statistically significant. Data: USGS 2014

Figure8. Data from the BBS suggest that great horned owl populations statewide have declined over time, although this trend is not statistically significant. Data: USGS 2014


Figure 9. Proportion of spotted owl sites in which barred owls and spotted owls were detected on the Oregon Coast Ranges Study Area, 1990-2012 Caption and Figure: Forsman et al. 2013

Figure 9. Proportion of spotted owl sites in which barred owls and spotted owls were detected on the Oregon Coast Ranges Study Area, 1990-2012 Caption and Figure: Forsman et al. 2013



Figure 10. Abundance trends (raw CBC count) for commonly sighted owl species in the Coos estuary. Data: Audubon 2014, Rodenkirk 2012; Bird Sketches: Csuti et al. 1997

Figure 10. Abundance trends (raw CBC count) for commonly sighted owl species in the Coos estuary. Data: Audubon 2014, Rodenkirk 2012; Bird Sketches: Csuti et al. 1997



Figure 11. BBS abundance data for songbird populations in Oregon showing clear abundance trends (1966-2012). Data: USGS 2014

Figure 11. BBS abundance data for songbird populations in Oregon showing clear abundance trends (1966-2012). Data: USGS 2014



Songbirds

This section summarizes data for “passerines,” meaning bird species of the order Passeriformes, commonly referred to as “songbirds.” Songbirds comprise a diverse group of many recognizable bird species (e.g., chickadees, tits, warblers, finches, thrushes, sparrows, etc.). Statewide abundance trends are presented briefly followed by a discussion of local songbird population trends. Emphasis is given to species that have displayed clear trends over time.

Songbirds in Oregon

The BBS indicates that 21 songbird species have shown statistically significant declines since 1966. Only 2 species have had statistically significant increase. Figure 11 summarizes the BBS data for 27 passerine species exhibiting clear population trends in Oregon since 1966.

Songbirds in the Lower Coos Watershed

Below we focus on passerine species in the lower Coos watershed that show strong evidence of changing populations:

Black Pheobe (Sayornis nigricans)

Black pheobes were not sighted during the local CBC from 1980-1995. However, starting in 1996, this species has been sighted every year and has become increasingly abundant (Figure 12).

Common Yellowthroat (Geothlypis trichas)

From 1980-2001, the Coos Bay CBC did not record any common yellowthroat sightings. Since 2002, the species has been sighted in the Coos estuary 5 times during the local CBC, and is now frequently found overwintering in several Coos County locations (Audubon 2014, Rodenkirk 2012)(Figure 13).

Figure 12. Coos Bay CBC data indicate that local midwinter black phoebe abundance has increased, with consistent sightings beginning in 1996 and increasing since then. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997

Figure 12. Coos Bay CBC data indicate that local midwinter black phoebe abundance has increased, with consistent sightings beginning in 1996 and increasing since then. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997


Figure 14. Cedar waxwings have been sighted in the Coos estuary during the CBC since 2006. Sightings have often occurred in greater numbers in recent years than they have in the past. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997

Figure 14. Cedar waxwings have been sighted in the Coos estuary during the CBC since 2006. Sightings have often occurred in greater numbers in recent years than they have in the past. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997


Figure 15. Coos Bay CBC swamp sparrow sightings have become more common since 1996. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012

Figure 15. Coos Bay CBC swamp sparrow sightings have become more common since 1996. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012











Fowl-like Birds

This section summarizes data for fowl-like birds of the order Galiformes that are closely associated with terrestrial habitats, including quail, pheasant, grouse, and turkey species. Statewide abundance trends are presented, followed by a discussion of songbird population patterns in the Coos estuary. Emphasis is given to species that have displayed clear trends over time.

Fowl-like Birds in Oregon

The BBS data indicate that two fowl-like bird species, including the wild turkey (Melegris gallopavo) and ring-necked pheasant (Phasianus colchicus), show clear abundance trends (1966-2013)(Figure 18). In Oregon, turkeys are becoming more abundant, while pheasants are becoming less abundant.

Yellow-breasted Chat (Icteria virens)

In 2012, a yellow-breasted chat was sighted at a feeder in Coos Bay, representing the first winter record of this species in Oregon (Cornu et al. 2012). This bird is a neotropical migrant, which means that its midwinter presence may be indicative of a changing climate, although more data are needed to determine if a cause and effect relationship exists (see Why is it happening?)

Cedar Waxwing (Bombycilla cedrorum)

The CBC has sighted cedar waxwings periodically from 1980-2005. However, beginning in 2006, local midwinter sightings have become more consistent and often more frequent (Figure 14).

Swamp Sparrow (Melospiza georgiana)

The local CBC rarely sighted swamp sparrows prior to 1996, but volunteers have recored sightings every year since then (Figure 15).

Red-winged Blackbird (Agelaius phoeniceus)

Red-winged blackbirds are historically abundant in the Coos estuary. This species has been sighted every year during the local CBC since 1980, but the frequency of sightings has increased overtime (Figure 16).

Sparrow species

Many sparrow species have been historically abundant in the Coos estuary. Six sparrow species have been sighted with increasing frequency during the local CBC, including the golden-crowned sparrow (Zonotrichia atricaplillia), house sparrow (Passer domesticus), song sparrow (Melospiza melodia), white-crowned sparrow (Zonotrichia leucophrys), white-throated sparrow (Zonotrichia albicollis), and Lincoln’s sparrow (Mesospiza lincolnii). Summary statistics describing trends in the raw CBC count for these six species are found in Table 2.

American Crow (Corvus brachyrhynchos), Common Raven (Corvus corax), and Stellar’s Jay (Cyanocitta Stelleri)

These three species belong to the family Corvidae and have shown clear increasing trends since 1980. All three birds are historically abundant in the Coos estuary, with multiple sightings occurring every survey year since 1980. CBC sightings are becoming more frequent and may indicate increasing abundance in the project area (Figure 17).

Other Common Songbirds

In addition to the songbird species mentioned above, there are many other passerines commonly found locally. Most of these species do not exhibit a clear abundance trend over time. Table 3 summarizes raw CBC data (1980-2013) for 27 of the most commonly counted songbirds in the lower Coos watershed.

Figure 13. Historically, the common yellowthroat has not been observed overwintering in the Coos estuary. However, the Coos Bay CBC has recorded a single sighting of common yellowthroat in 2002, 2003, 2006, 2008, 2011, and 2012. Data: Audubon 2014, Rodenkirk 2012; Photo credit: Gerrit Vyn taken from Cornell 2014

Figure 13. Historically, the common yellowthroat has not been observed overwintering in the Coos estuary. However, the Coos Bay CBC has recorded a single sighting of common yellowthroat in 2002, 2003, 2006, 2008, 2011, and 2012. Data: Audubon 2014, Rodenkirk 2012; Photo credit: Gerrit Vyn taken from Cornell 2014


Figure 16. Red-winged blackbirds continue to be abundant in the Coos estuary. Midwinter sightings have become more common, suggesting that the species may be increasing abundant over time. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997

Figure 16. Red-winged blackbirds continue to be abundant in the Coos estuary. Midwinter sightings have become more common, suggesting that the species may be increasing abundant over time. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997




Fowl-like birds in the Lower Coos Watershed

The California quail (Callipepla californica) is the only fowl-like bird that is sighted nearly every year during the local CBC. Raw CBC counts for this species indicate no clear abundance trend (Figure 19). In addition to the California quail, ring-necked pheasant and ruffed grouse (Bonasa umbellus) have been sighted on rare occasions (i.e., 1-3 sightings periodically from 1983-2003). Mountain quail (Oreortyx pictus) was counted in 2006-2008 ( < 10 sightings annually). Historically, wild turkeys have not been counted during the local CBC. However, the CBC in 2011, 2012, and 2013 reported 28, 10, and 12 turkey sightings, respectively. More data are needed to determine if these sightings are indicative of a trend (e.g., increasing local abundance or range expansion). Figure 20 summarizes the raw CBC data for all fowl-like birds observed in the study area from 1980-2013.

Table 2. Six species of commonly occurring sparrow species have been counted with increasing frequency during the Coos Bay CBC. This table summarizes that trend by comparing average raw CBC count for two time periods (1980-1994 and 1995-2013). Time series graphs (right) showing increasing trends (1980-2013) are also presented. Data: Audubon 2014, Rodenkirk 2012; Photos: Cornell 2014

Table 2. Six species of commonly occurring sparrow species have been counted with increasing frequency during the Coos Bay CBC. This table summarizes that trend by comparing average raw CBC count for two time periods (1980-1994 and 1995-2013). Time series graphs (right) showing increasing trends (1980-2013) are also presented. Data: Audubon 2014, Rodenkirk 2012; Photos: Cornell 2014



Figure 17. Coos Bay CBC data indicate that local midwinter abundance of three “corvids,” including the American crow, common raven, and Stellar’s jay, has shown a clearly increasing trend since 1980. Raw CBC count for these species is indexed relative to 1980-levels above (1980=100). Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89).  Data: Audubon 2014, Rodenkirk 2012; Bird Sketches: Csuti et al. 1997

Figure 17. Coos Bay CBC data indicate that local midwinter abundance of three “corvids,” including the American crow, common raven, and Stellar’s jay, has shown a clearly increasing trend since 1980. Raw CBC count for these species is indexed relative to 1980-levels above (1980=100). Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketches: Csuti et al. 1997



Table 3. Many passerines do not exhibit any clear abundance trends in the lower Coos watershed. This table summarizes raw CBC data for some of the most commonly occurring songbirds in the Coos estuary. Time series graphs (right) showing increasing trends (1980-2013) are also presented. Data: Audubon 2014, Rodenkirk 2012; Photos: Cornell 2014

Table 3. Many passerines do not exhibit any clear abundance trends in the lower Coos watershed. This table summarizes raw CBC data for some of the most commonly occurring songbirds in the Coos estuary. Time series graphs (right) showing increasing trends (1980-2013) are also presented. Data: Audubon 2014, Rodenkirk 2012; Photos: Cornell 2014



Figure 20. Observations of fowl-like species during the CBC (1980-2013). More frequent observation corresponds to darker blue. Raw count data for each year are indicated (number). “CW” means the species was present during the CBC week, but it was not observed during the count. Data: Audubon 2014, Rodenkirk 2012

Figure 20. Observations of fowl-like species during the CBC (1980-2013). More frequent observation corresponds to darker blue. Raw count data for each year are indicated (number). “CW” means the species was present during the CBC week, but it was not observed during the count. Data: Audubon 2014, Rodenkirk 2012



Doves and Pigeons

This section summarizes data for birds of the order Columbiformes, which are commonly known as doves and pigeons. Regional data are presented at a statewide level using breeding population estimates as a proxy for abundance, followed by a discussion of Coos estuary data, which use CBC sightings to project trends in local abundance. The local data section highlights dove and pigeon species that display the most apparent trends since the 1980s.

Doves and Pigeons in Oregon

The BBS data indicate that only the mourning dove (Zenaida macroura) shows a clear abundance trend (decreasing abundance) at the regional level (1966-2013)(Figure 21).

Doves and Pigeons in the Coos Estuary

Below we focus on Dove and Pigeon species in the lower Coos watershed that show strong evidence of changing populations:

Eurasian Collared Dove (Streptopelia decaocto)

The Eurasian Collared Dove was first sighted during the CBC in 2007 (Audubon 2014, Rodenkirk 2012). Since then, they have become increasing abundant; CBC sightings have increased notably (Audubon 2014, Rodenkirk 2012)(Figure 22).

Band-tailed Pigeon (Patagioenas fasciata)

Band-tailed pigeons were sighted in three mid-1980s CBC’s and again from 1998-2009 (Aubuon 2014). They have not been counted during the CBC since 2009; scientists indicate they’re very rarely sighted in the winter (Audubon 2014, Rodenkirk 2012).

Figure 19. Raw CBC count for California quail in the lower Coos watershed. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012

Figure 19. Raw CBC count for California quail in the lower Coos watershed. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012



Figure 22. Raw CBC count for Eurasian collared-dove (1980-2013). Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012

Figure 22. Raw CBC count for Eurasian collared-dove (1980-2013). Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012





Hummingbirds

This section summarizes available data for hummingbird species of the order Apodiformes that have shown clear abundance trends either statewide or locally.

Hummingbirds in Oregon

The BBS data show a clear abundance trend over time for the rufous humingbird (Selasphorus rufus), which appears to be decreasing in abundance (Figure 23).

Hummingbirds in the Coos Estuary

Anna’s hummingbird (Calypte anna) is the only hummingbird species regularly sighted during the Coos Bay CBC. The frequency of Anna’s hummingbird midwinter sightings has increased over time, suggesting the species is becoming more locally abundant (Figure 24).

Figure 21. BBS abundance data for the mourning dove (Zenaida macroura) in Oregon. This species is the only dove species showing a clear abundance trend (1966-2012) in the BBS data. Data: USGS 2014

Figure 21. BBS abundance data for the mourning dove (Zenaida macroura) in Oregon. This species is the only dove species showing a clear abundance trend (1966-2012) in the BBS data. Data: USGS 2014





Woodpeckers

This section summarizes available data for birds of the order Piciformes, which are commonly referred to as woodpeckers, sapsuckers, and flickers. The data summary focuses on birds that have shown clear abundance trends either statewide or locally.

Woodpeckers in Oregon

The BBS data indicate that five woodpecker species of have shown clear abundance trends statewide since 1966 (Figure 25). Pileated woodpeckers, yellow-bellied sapsuckers, and re-breasted sapsuckers appear to be increasing in abundance over time, while northern flickers, and red-naped sapsuckers appear to be decreasing in abundance in Oregon.

Woodpeckers in Lower Coos Watershed

Several woodpecker species are commonly sighted in the Coos estuary. However, it’s difficult assess any abundance trends. CBC sightings of some species (e.g., northern flicker) are rare and do not show any apparent trend. Table 4 summarizes the raw CBC data for woodpecker species in the Coos estuary.














Why is it happening?

Multiple factors can often work together to determine local bird abundance trends (e.g., land use changes occurring simultaneously with climate anomalies may work to the detriment of some species while favoring others). Similar to aquatic birds, some terrestrial bird species are highly migratory. Therefore, factors affecting distant habitats may affect bird species survival rates which will be reflected in local abundance data.

Birds expand their ranges when the resources they rely on for survival become available to them in different geographic areas (Cornu et al. 2012). Habitat alterations related to human activities and climate change are also leading factors in bird range expansions (Askins 2000). This might explain the range expansions of black pheobes and red-shouldered hawks, which have moved northward toward Tillamook County and east to the Williamete Valley over the past 30 years (T. Rodenkirk, pers. comm., January 19, 2012).

Human population growth and urban development may benefit birds in some cases (Cornu et al. 2012). Peery and Henry (2010) explain that “The expansion of human activities into rural areas and natural landscapes has resulted in widespread increases in the abundance of synanthropic species (birds that live near humans and benefit from an association with human habitat).” In fact, some birds that have the ability to adapt to a wide range of habitat conditions (e.g., crows, ravens) have been observed in higher density in urban settings (Kelly et al. 2002). Doves and pigeons are also famously synanthropic species. The Eurasian collared-dove, an introduced species, was first recorded in Oregon in 1999 (Cornu et al. 2012). By 2006, Eurasian collared-doves had established themselves in all 36 Oregon counties, including Coos (R. Namitz, pers. comm., January 19, 2012; T. Rodenkirk, pers. comm., January 19, 2012).

In some cases, active habitat management and restoration have resulted in species recoveries. Similar to the brown pelican (see Aquatic birds), the bald eagle and peregrine falcon have benefited from the efforts of volunteers and avian professionals alike (Cornu et al. 2012). In both cases, the effort has been substantial enough to remove the species from the federal Threatened and Endangered Species List (USFWS 2014).

Some evidence suggests that the overwintering population of neotropical migrants (e.g., common yellowthroats, orange-crowned warblers, and yellow-breasted chats) in Coos County may be increasing (R. Namitz, pers. comm., January 19, 2012; T. Rodenkirk, pers. comm., January 19, 2012; Rodenkirk 2012a; Audubon 2014). Neotropical migrants are birds that spend the summer in the northern temperate and polar latitudes and migrate south to the tropics where climate and food availability is more agreeable in the winter months (Cornu et al. 2012). This trend could be indicative of a general warming pattern in the temperate latitudes, although more data are needed to determine the exact correlation between climate change and neotropical migrant abundance.

Figure 18. BBS abundance data for fowl populations in Oregon showing clear trends (1966-2012). Data: USGS 2014

Figure 18. BBS abundance data for fowl populations in Oregon showing clear trends (1966-2012). Data: USGS 2014









Figure 24. Raw CBC data (1980-2013) suggest that local populations of Anna’s hummingbird may be increasingly abundant. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997

Figure 24. Raw CBC data (1980-2013) suggest that local populations of Anna’s hummingbird may be increasingly abundant. Data gaps occur during years in which the CBC was not conducted (2010) or not reported (1987-89). Data: Audubon 2014, Rodenkirk 2012; Bird Sketch: Csuti et al. 1997



Figure 23. BBS abundance data for the rufous hummingbird, the only hummingbird species showing a clear abundance trend statewide (1966-2013). Data: USGS 2014

Figure 23. BBS abundance data for the rufous hummingbird, the only hummingbird species showing a clear abundance trend statewide (1966-2013). Data: USGS 2014















Figure 25. BBS abundance data for woodpecker species that have shown clear abundance trends statewide (1966-2013). Data: USGS 2014

Figure 25. BBS abundance data for woodpecker species that have shown clear abundance trends statewide (1966-2013). Data: USGS 2014


Habitats availability also influences local abundance trends. The Coos estuary and associated uplands represent important breeding, foraging, and roosting habitats for many bird species. As habitats are lost or restored, bird distributions may shift to reflect changes in the availability of important resources (e.g., food/prey, cover, etc.) and changes in the presence/absence of predators.


Background

Oregon’s total wildlife diversity accounts for more than 42% of all terrestrial vertebrates in the United States and Canada (Csuti et al. 1997). Birds species comprise much of that diversity; many remain in Oregon year-round and others visiting the state during migration.

Because birds use the lower Coos watershed and estuary for a variety of activities (breeding, nesting, roosting, foraging, etc.), trends in local bird abundance and migration timing can signal important changes to habitat availability or suitability; these habitat changes have the potential to affect both birds and other wildlife (Cornu et al. 2012). Birds can often be considered “indicator species,” because changes in their status can provide an early warning about less detectable trends in local environmental conditions.

Changes in the abundance of one bird species can sometimes directly affect other species. For example, the range expansions of the northern barred owl are likely to negatively affect local populations of northern spotted owls (see Birds of Special Concern data summary in this chapter). However, this kind of direct cause/effect relationship doesn’t always exist. In the case of the Eurasian collared-dove, some concern exists about competitive pressures on native mourning doves (Zenaida macroura). However, research suggests that although the two species have similar diets, the Eurasian collared-dove “does not appear more behaviorally aggressive or competitively successful than mourning doves” (Poling and Hayslette 2006).

Table 4. This table summarizes raw CBC data for some of the most commonly occurring woodpeckers in the Coos estuary. Time series graphs (right) showing increasing trends (1980-2013) are presented. Data: Audubon 2014, Rodenkirk 2012; Photos: Cornell 2014

Table 4. This table summarizes raw CBC data for some of the most commonly occurring woodpeckers in the Coos estuary. Time series graphs (right) showing increasing trends (1980-2013) are presented. Data: Audubon 2014, Rodenkirk 2012; Photos: Cornell 2014


References

Askins, R. A. 2000. Restoring America’s Birds: Lessons from Landscape Ecology. New Haven and London: Yale University Press.

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