Peregrine falcon (pealei and anatum/tundrius) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Search effort

Beginning in 1970, a national survey of breeding Peregrine Falcons has been conducted every five years in selected areas throughout southern Canada (Cade and Fyfe 1970; Fyfe and Olendorff 1976; Murphy 1990; White et al. 1990; Holroyd and Banasch 1996; Rowell et al. 2003; Banasch and Holroyd 2004; U. Banasch personal communication (pers. comm.) 2006). In addition to the broad-scale national surveys conducted, several provinces and territories conduct their own surveys more frequently in selected areas.

The national surveys, which are designed to collect population and productivity trend information, provide a minimum breeding population size only. This is because they occur at select sites so many areas are not surveyed. Many additional breeding pairs exist, especially Tundrius Peregrines Falcons that breed in a vast, relatively uninhabited Arctic landscape.

Abundance

Although there were no systematic surveys of Peregrine Falcons in North America before their decline, the pre-collapse population of all three subspecies has been estimated at 7,000-8,000 breeding pairs (Rowell 2002). By the late 1990s, an estimated 2,500-3,000 pairs of Anatum, 2,300-3,000 pairs of Tundrius and 850-1,000 pairs of Pealei Peregrine Falcons were thought to breeding in North America (White et al. 2002).

Based on information from the 2005 national surveys, the minimum population size for Anatum Peregrine Falcons in Canada is 969 adult birds (464 pairs + 41 single birds = 505 occupied sites; Table 8). Similar survey information for Tundrius Peregrine Falcons shows a total of 94 adult birds (46 pairs + 2 single birds = 48 occupied sites; Table 8) in 2005. If the 105 birds from the most recent surveys at sites generally involved in the national survey, but not checked in 2005 (Ungava Bay (34 pairs), Tuktut Nogait (18 pairs + 1 single bird); Table 8) are added, then the minimum population size for Tundrius Peregrine Falcons is 199 adult birds. Together, a minimum population size for Anatum/Tundrius Peregrine Falcons in Canada is 1168 mature individuals. National survey information for Pealei Peregrine Falcons shows a total of 176 adult birds (67 pairs + 42 single birds = 109 occupied sites; Table 8) in 2005.

As mentioned earlier, population estimates based on national survey information will underestimate the total population of Peregrine Falcons. This is especially the case for Tundrius Peregrine Falcons. For example, surveys conducted by Nunavut (NU) and Northwest Territories (NT) governments, along with smaller surveys conducted by the Canadian Wildlife Service and private firms, have found 502 nest sites (approximately 1000 birds; see Appendix A), in addition to national survey sites, that have been occupied at some point since the 1980s (GNWT/GNDoE unpublished data; courtesy of S. Carrière). Thus, the numbers for Tundrius are likely closer to several thousand birds (G. Holroyd pers. comm. 2006).

These populations also have the potential to increase in size, given that other conditions, such as food supply, remain stable and because a number of historic breeding sites remain unoccupied. For example, in Alberta, at least 115 natural historically used Anatum Peregrine nest sites are known, and more likely exist (Alberta Peregrine Falcon Recovery Team 2004), but only 48 are occupied. Similarly, in British Columbia, where there are about 232 known Pealei Peregrine Falcon nest sites (Cooper 2006), only one half are occupied.

Fluctuations and trends

Peregrine populations have recovered considerably in the last two decades because of the ban on DDT, reintroductions of Anatum Peregrine Falcons, and increased natural productivity (Kiff 1988; Enderson et al. 1995; Millsap et al. 1998). In Canada, most areas with good survey effort have shown a substantial increase in Anatum and Tundrius Peregrine Falcons since 1970 (Table 8), with tremendous increases between 2000 and 2005 in some areas (e.g. 43% increase in occupied sites in southern Ontario, 107% in southern Quebec). Increased search effort also contributed to the increasing population trends. Pealei Peregrine Falcons, which did not undergo the declines experienced by the other subspecies, increased slightly during this time period (Table 8).

Table 8. Number of sites occupied by Peregrine Falcons in selected areas surveyed inCanada1970-2005. Numbers in parentheses indicate number of sites occupied by territorial pairs, while the first number includes sites with pairs and with single birds (Rowell et al. 2003). Data for 2005 from U. Banasch (pers. comm.).
Species Area 1970 1975 1980 1985 1990 1995 2000 2005
Anatum Labrador, Newfoundland
2(2)
0
nd
2(2)
21(21)
31(31)
22(15)
28(18)
Anatum Bay of Fundy (NS,NB)
0
0
0
1(1)
7(5)
6(6)
11(11)
20(16)
Anatum Southern Quebec
0
nd
1(1)
1(1)
15(12)
15(13)
28(25)
58(53)
Anatum Southern Ontario
0
0
0
1(0)
3(2)
15(14)
53(42)
76(67)
Anatum Southern Manitoba
nd
nd
0
1(1)
2(1)
4(4)
3(2)
3(2)
Anatum Southern Saskatchewan
0
nd
0
2(1)
2(1)
2(2)
4(3)
1(0)
Anatum Alberta south of 58
1(1)
0
0
2(2)
3(3)
13(12)
23(23)
21(17)
Anatum South Interior BC
nd
nd
nd
nd
nd
2(2)
1(1)
4(2)
Anatum Lower Mainland BC
nd
nd
nd
nd
nd
8(8)
6(5)
Anatum Gulf Islands/se Vancouver Island, BC
nd
nd
4(2)
9(7)
11(9)
12(9)
Anatum Alberta North of 58
2(1)
3(3)
9(9)
6(5)
9(9)
23(23)
29(29)
31(31)
Anatum Porcupine River, Yukon
nd
8(8)
16(13)
14(11)
36(nd)
29(29)
35(35)
30(30)
Anatum Peel River, Yukon
nd
nd
18(12)
12(10)
14(nd)
37(37)
22(22) Table noteg
22(22) Table noteg
Anatum Yukon River, Yukon
6(5)
6(5)
12(10)
22(18)
33(nd)
46(46)
46(46)
77(77)
Anatum Southern Lakes, Yukon
 
 
 
 
 
1(1)
nd
2(2)
Anatum Mackenzie Valley, NT
9(6)
24(21)
20(15)
45(nd)
88(77)
83(83)
80(80)
113(113)
Anatum Total/average
20(15)
41(37)
81(64)
113(54)
239(134)
324(318)
374(348)
505(464)
Tundrius Ungava Bay, Quebec
12(9)
11(9)
10(10)
23(23)
34(34)
nd
nd
nd
Tundrius North Slope, Yukon
nd
5(5)
2(0)
0
1(0)
5(5)
9(9)
19(19)
Tundrius Rankin Inlet, Nunavut
nd
nd
26(nd)
26(26)
27(27)
25(22)
29(27)
Tundrius Tuktut Nogait NP, NT
 
 
 
 
19(19) Table notei
 
19(18)
nd
Tundrius Total/average
12(9)
16(14)
20(18)
49(23)
80(79)
32(32)
53(49)
48(46)
Pealei Langara Island
6(5)
6(6)
6(6)
6(5)
7(7)
7(5)
9(7)
10(8)
Pealei Queen Charlotte Islands
56(46)
60(51)
73(58)
50(nd)
64(53)
62(45)
60(44)
74(46)
Pealei N. Vancouver Island/ Scott Islands
nd
nd
nd
6(5)
10(5)
10(6)
20(12)
18(13)
Pealei Triangle Island
nd
nd
nd
nd
nd
8(8)
7(6)
7(nd)
Pealei Total/average
62(51)
66(57)
79(64)
62(10)
81(65)
87(64)
96(69)
109(67)

Anatum Peregrine Falcon

Anatum Peregrine Falcons have generally returned to near historical (pre-DDT) numbers in most regions of Canada, with the 2000 and 2005 surveys confirming that most populations are stable or increasing (e.g. Rowell et al. 2003; U. Banach pers. comm. 2006). Overall, occupied sites increased from 20 in 1970 to 505 in 2005, which is a 25-fold increase in numbers (Table 8). Occupied sites increased by 35% alone from 2000 to 2005. Of note is that interim goals for national territory occupancy and productivity set in the Anatum Peregrine Falcon Recovery Plan (Erickson et al. 1988), were met by 1995 (Banasch and Holroyd 2004).

The extent of increases from 1970-2005 is striking in many regions (Table 8). For example, Labrador has gone from 2 to 28 known sites. Most areas occupied 75-150 years ago are occupied now, although no information exists on whether or not those birds disappeared during the DDT era (J. Brazil pers. comm. 2006). Occupancy of inland sites in Labrador have, however, decreased since 1999 (J. Brazil pers. comm. 2006). In southern Quebec, occupied sites went from 0 in 1970 to 58 by 2005 (Poulin et al. 2006). Similarly, southern Ontario went from 0 to 76 occupied sites during the same time period, and may not yet be at pre-DDT levels (A. Dextrase pers. comm. 2006), although lack of historic data precludes confirmation. Populations remain very small in the southern prairies through 2005, although the number of pairs is higher in the last two decades than previously known. In Alberta, where fostering of captive bred birds has strongly influenced population increases (Stepnisky 1998), Anatum numbers have remained stable since 2000 (Alberta Peregrine Falcon Recovery Team 2004). In the Mackenzie Valley, NT, occupied sites have increased from 9 in 1970 to 113 in 2005.

In British Columbia, Anatum Peregrine Falcons are increasing on the coast but interior populations seem to be holding at low levels. The historical decline of Anatum Peregrine Falcons in interior British Columbia significantly pre-dated the DDT crisis. In the Okanagan valley, there were at least 15 nest sites in use in 1906-1907. One cliff near Vaseux Lake was reported to contain three active Peregrine Falcon nests in one year (Cannings et al. 1987). By 1922, all or almost all of these nest sites were inactive and Peregrine Falcons were absent from the valley (Taverner 1922). The status of most other historically known Anatum Peregrine nest sites elsewhere in the interior of British Columbia remains uncertain during the 1940s to the 1980s, but most were unoccupied in the mid-1990s (Cooper 1998).

Reintroductions

The numbers of captive-raised Anatum Peregrines released in Canada are impressive: e.g. 178 in the Bay of Fundy (1982-1991; Amirault 2004), 255 in Quebec (1976-1994; Berthelot et al. 2002), 524 in Ontario (1977-1996; Royal Ontario Museum 2004), 103 in Manitoba (1981-2001; Sliworsky and Nero 2003) and about 250 in Alberta (1975-1985; Rowell and Stepnisky 1997). About 1,500 pure Anatum Peregrine Falcons have been released in Canada (G. Holroyd pers. comm. 2006) and these releases have led to the restoration of breeding Anatum populations in many areas. 

Tundrius Peregrine Falcon

Breeding populations of Tundrius Peregrine Falcons appear to have recovered to near pre-collapse numbers, with significant increases between 1970 and 2005 (White et al. 2002; Table 8). Increases in some areas were exponential through the 1980s (Shank et al. 1993). Tundrius Peregrine Falcon numbers in Kugluktuk and Hope Bay, NU were showing upward trends until the surveys ceased in 1996 (Figure 3). In 2005, Tundrius Peregrine Falcons from two survey areas reached all-time highs (Table 8); however, only one of 32 occupied sites in Rankin Inlet was productive, which was an all-time low (M. Setterington pers. comm. 2006). The latter was explained, however, by mortality of eggs/young caused by severe rain-storms in early summer.Although the Ungava Bay area of Quebec was not surveyed from 1995-2005 (Table 8), a partial survey by the Canadian Wildlife Service in 2000 found 18 occupied sites suggesting that the species is still present in this area. Population increases in Canada parallel steady increases in Greenland Tundrius populations (e.g. Mattox and Seeger 1988).

Figure 3. Number of occupied Tundrius Peregrine Falcon territories in Rankin Inlet (530 km², early June surveys), Hope Bay area (2000 km² early to mid-July surveys) and Kugluktuk (4000 km², early to mid-July surveys), Nunavut. Data points not joined by lines indicate that no data were collected in those years (Source: M. Setterington).

Figure 3. Number of occupied Tundrius Peregrine Falcon territories in Rankin Inlet (530 km², early June surveys), Hope Bay area (2000 km² early to mid-July surveys) and Kugluktuk (4000 km², early to mid-July surveys), Nunavut

Pealei Peregrine Falcon

Pealei Peregrine Falcon populations in Canada are currently increasing (Cooper 2006). In British Columbia, 96 occupied territories were estimated in 2000 versus 87 occupied territories for the mid-1990s. In 2005, Pealei Peregrine Falcons were at their highest level of occupancy (109; Cooper 2006) since before the 1970s (Table 8). On the Queen Charlotte Islands, there were 74 occupied nest sites in 2005, which is the highest number recorded since 1980 (Table 8). In 2000, Pealei Peregrine Falcons were thought to be increasing on northern Vancouver Island (Rowell et al. 2003) as occupied nest sites reached 20; followed by 25 occupied nest sites in 2005 (Table 8).

Pealei Peregrine Falcon avoided precipitous population declines from chemical pesticide contamination. Their non-migratory habits and reliance on remote seabird populations for their food probably saved them from exposure to high levels of DDT, even though recent studies show the continued persistence of organochlorines in seabird tissue within the range (Alaska panhandle) of Pealei Peregrine Falcons (Becker et al. 2003).

Rescue effect

The potential for immigration of Peregrine Falcons is high for Anatum and Peale’s Peregrines. Anatum Peregrine Falcons in the US, which serve as a potential source of immigrants for Canada, are increasing, and have recently been delisted. It is worth noting, however, that some immigrants from the USA may not be of native stock. By 2002, about 2,000 pairs of Anatum Peregrine Falcons were thought to exist in the USA (USFWS 2003) and current (2004) numbers are undoubtedly higher. There is some evidence that immigration from the US occurs. For example, there are two known Anatum Peregrine Falcons breeding in coastal British Columbia that were banded as nestlings in the San Juan Islands, Washington (D. Doyle pers. comm. 2004). Similarly, a known Peregrine Falcon hatched in the US was observed in New Brunswick in 2006 (D. Amirault pers. comm. 2006), and anadult female breeding on the Bow River in southern Alberta originally fledged from a site in Great Falls, Montana (G. Court pers. comm. 2006). In addition, the success of the introductions through hacking of young birds suggests the potential for rescue is very high.

Most of the world’s Tundrius Peregrine population occurs in Arctic Canada, but Tundrius Peregrine Falcons from Greenland are known to migrate through Canada; therefore, some potential for rescue exists.

Pealei Peregrine Falcons in the USA also appear to be stable. Surveys in the mid- 1990s found 271 active nest sites in Alaska, 17-20 in Washington and 5-10 in Oregon, although some of the Washington and Oregon birds may not be Peale’s (Wilson et al. 2000; White et al. 2002).

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