High Elevation Landbird Program
5-year report
Greg Campbell1, Becky Whittam1 and Greg Robertson2
April 2007
1
Bird Studies Canada – Atlantic Region
P.O. Box 6227, Sackville, NB E4L 1G6
2
Environment Canada
6 Bruce St., Mount Pearl, NL A1N 4T3
The Government of Canada Habitat
Stewardship Program for Species At Risk
Introduction
The Bicknell’s Thrush is one of the rarest songbirds in North America, with a world-wide
population estimated at 25,000 to 50,000 individuals (Rimmer et al. 2001). It was recently
designated as the landbird of highest conservation priority in Bird Conservation Region 14 by
Partners in Flight. It is listed as a Species of Special Concern by COSEWIC, and designated as
May be at Risk in New Brunswick, as Sensitive in Nova Scotia and as Globally Vulnerable by
the World Conservation Union (IUCN; Stattersfield and Capper 2000). These designations are
due to the species’ fragmented population distribution and to a lack of understanding of its
breeding biology and habitat requirements.
Bicknell’s Thrush typically breed in dense, stunted coniferous forests typical of high elevation
areas in eastern Canada (Quebec, New Brunswick and Nova Scotia) and the northeastern United
States (Connolly et al. 2002, Lambert et al. 2005). This habitat is threatened by several factors,
including climate change, acid rain, mercury deposition and forestry operations, the latter
occurring mainly in Canada (Chisholm 2005, Gardiner 2006) and on the species Hispaniola
wintering grounds (Latta et al. 2003, Rimmer et al. 2001, Rimmer et al. 2005). In addition to
occurring in their “traditional” habitat, Bicknell’s Thrushes have also been found to inhabit
regenerating clear cuts in Canada (Ouellet 1993, Nixon et al. 2001, Connolly et al. 2002,
Chisholm 2005, Gardiner 2006); however, breeding in this type of habitat, while it is expected to
occur, has not been officially documented in the Maritime provinces despite work by Chisholm
(2005) and Gardiner (2006).
Breeding populations of Bicknell’s Thrush once existed in several coastal areas in the Maritimes,
such as on Grand Manan Island in New Brunswick, and Cape Fourchu, Seal Island and Mud
Island in Nova Scotia (Rimmer et al. 2001). Surveys conducted in 1997 by the Canadian Wildife
Service also detected Bicknell’s Thrush on St. Paul Island and Scaterie Island in Nova Scotia (D.
Busby pers. comm.).
Since 2002, Bird Studies Canada’s High Elevation Landbird Program (HELP) has been
monitoring populations of Bicknell’s Thrush and other high elevation birds in New-Brunswick’s
central and western highlands as well as in Cape Breton, Nova Scotia. Two routes were also
added in Prince Edward Island in 2005. Unlike the routes in New Brunswick and Nova Scotia,
these new routes are at elevations of less than 50 meters.
This report highlights results from the 2006 HELP field season and includes an analysis of fourand five-year trends in high elevation landbird species in the Maritimes.
Methods
Survey Protocol
A total of 71 routes were surveyed in 2006, 43 in New Brunswick (Figure 1), 26 in Nova Scotia
(Figure 2) and 2 in Prince Edward Island (at East Point and North Cape). Volunteers conducted
surveys on eight of the routes, while the remaining 63 were done by BSC staff.
Figure 1. HELP survey routes in New Brunswick. Sub-regions are clearly visible based on
clustering of routes in North-central NB around Mount Carleton Provincial Park and extreme
Northwestern NB.
Figure 2. HELP survey routes in Cape Breton, Nova Scotia. Shading represents Cape Breton
Highlands National Park.
Each route consists of five stops spaced 250 m apart. Surveys started approximately 45 minutes
before sunrise and/or 30 minutes before sunset between June 4th and 26th. Surveyors listened for
ten minutes at each station and marked the approximate position of all Bicknell’s Thrush,
Swainson’s Thrush, Winter Wren, Blackpoll Warbler, Fox Sparrow and White-throated Sparrow
heard or seen in relation to the surveyor’s standing point at the center of a 50 m radius.
Observers noted whether the bird was singing and/or calling, and from which distance and
direction it was detected. Observers also recorded any red squirrels detected at each stop.
Surveys were not conducted in wind levels greater than four on the Beaufort scale or in
conditions of more than trace amounts of precipitation.
If no Bicknell’s Thrushes were detected by the end of the last point count, a playback protocol
was conducted immediately. This protocol consisted of playing one minute of Bicknell’s Thrush
playback, followed by three minutes of silent listening at each of the five stations in reverse
order until a Bicknell’s Thrush was detected or all stops were revisited. Data collected through
this protocol are used for presence/absence only and are not included in trend analyses.
Data Analysis
1. Frequency of occurrence and relative abundance
Frequency of occurrence and relative abundance were calculated for each of the target species in
2006 as a means of summarizing the data. Frequency of occurrence is obtained by dividing the
number of routes where the species was detected by the total number of routes surveyed.
Relative abundance is defined as the mean number of individuals of the target species per route
and is calculated by dividing the total number of individuals detected by the number of routes
surveyed.
2. Trend analyses
Trend analyses were also conducted for each of the target species. Trend analyses for Swainson’s
Thrush, Blackpoll Warbler and Fox Sparrow include data from all 5 years of monitoring. For the
White-throated Sparrow and Winter Wren, only four years of data were available as they were
not monitored during the first year of the program. Analyses for Bicknell’s Thrush also include
only four years of data due to a protocol change implemented after the first year. The original
(2002) protocol included 30 seconds of Bicknell’s Thrush playback in the middle of the 10
minutes of silent listening. This 30 second playback was removed in 2003 in order to harmonize
methods with the Vermont Institute of Natural Science’s Mountain Birdwatch program (Hart and
Carroll, 2004). See Appendix A for an analysis of five years of Bicknell’s Thrush data using a
partial HELP data set (i.e. first five minutes of protocol only, 2002-2006).
To examine trends in bird species abundance along routes standard log-linear regressions were
used. Counts were log-transformed, after adding 0.23 to correct for stops where zero birds were
counted. Stops were treated as subjects (or repeated measures), to address the fact that
observations were conducted at the same sites each year, and to remove among-stop variance
from the analysis of trends. Transformed counts were then analysed with standard regression
procedures, assuming normality of errors to calculate instantaneous rates of increase (r) with
associated error (SE). Annual rates of change (in %) are also presented, and calculated from r.
The data set was also divided into two groups within each province, to see whether trends were
similar between north-western New Brunswick and north-central New Brunswick, and between
Cape Breton Highland National Park and other Nova Scotia sites (using ANCOVA).
Finally, a second method was also used to examine trends in Bicknell’s Thrush along survey
routes. The change in the number of stops at which Bicknell's Thrush were detected was
calculated, in each of the four sub-regions. This was done with logistic regressions, with stop
treated as a subject (or repeated measure).
Results
Frequency and Abundance in 2006
Bicknell’s Thrush was found on 16 of the 43 routes in New Brunswick in 2006. Of these routes,
10 had detections during the silent point count period, and the other six routes detected
Bicknell’s Thrush only during the playback period. In Nova Scotia, seven of 26 routes detected
Bicknell’s Thrush, two during the playback period. No Bicknell’s Thrush were detected in Prince
Edward Island.
Table 1: Frequency of occurrence (% routes with species) and relative abundance (average birds/route) for HELP
target species on all routes run in 2006. Bicknell’s Thrush numbers include birds heard during both silent listening
and after playback.
Species
NB (n = 43)
NS (n = 26)
PE (n = 2)
Bicknell’s Thrush
Frequency
37.2
27
0
Abundance
0.63
0.27
0
Blackpoll Warbler Frequency
46.5
61.5
0
Abundance
1.55
1.50
0
Fox Sparrow
Frequency
76.7
57.6
0
Abundance
1.93
2.07
0
Swainson’s Thrush Frequency
100
88.4
50
Abundance
13.5
5.96
3.5
White-throated
Frequency
97.6
92.3
0
Sparrow
Abundance
9.58
5.57
0
Winter Wren
Frequency
67.4
15.3
0
Abundance
1.79
0.27
0
Trends 2002-2006
1. Trends by province
The number of Bicknell’s Thrush reported on survey routes has been declining annually at a rate
of 6.9% in New Brunswick and 9.3% in Nova Scotia over the survey period. White-throated
Sparrow has also been declining annually at a rate of 8.4% in New Brunswick and 5.2% in Nova
Scotia (Table 2). Trends among other species were variable: Blackpoll Warbler showed
significant increases in both areas (approximately 4-5% annually), trends for both Swainson’s
Thrush and Fox Sparrow showed no significant change in New Brunswick but significant
increases in Nova Scotia, and Winter Wren showed a significant increase in New Brunswick but
no significant change in Nova Scotia.
Table 2. Results of trend analyses for New Brunswick and Nova Scotia. Results for Bicknell’s Thrush, Winter Wren
and White-throated Sparrow are from 2003-2006. Results for Blackpoll Warbler, Fox Sparrow and Swainson’s
Thrush are from 2002-2006. r is the instantaneous rate of change. Significant rates of change (P<0.05) are
highlighted in grey.
Nova Scotia
New Brunswick
%annual
%annual
SE
r
SE(r) change
SE (%)
r
SE(r)
change
(%)
Bicknell’s
Thrush
-0.072
0.021 -6.9
1.9
-0.098
0.024
-9.3
2.2
Blackpoll
0.038
0.015 3.9
1.6
0.051
0.022
5.2
2.3
Warbler
Fox Sparrow
0.045
0.023
4.6
2.4
0.004
0.019 0.4
1.9
Swainson’s
Thrush
0.078
0.032
8.1
3.4
0.028
0.021 2.8
2.2
Winter Wren
0.081
0.026 8.4
2.9
-0.022
0.019
-2.2
1.9
White-throated
-0.088
0.031 -8.4
2.9
-0.053
0.043
-5.2
4.0
Sparrow
2. Trends by sub-region
Bicknell’s Thrush was the only species found to be declining significantly in all four subregions. Declines in White-throated Sparrows were less evident in sub-regions, as the only
significant decline was seen in north-central New Brunswick. In Cape Breton Highlands
National Park Bicknell’s Thrush and Winter Wren declined significantly, while all other species
showed non-significant declines. Outside of the park Blackpoll Warbler, Fox Sparrow, and
Swainson’s Thrush showed significant increases.
Table 3. Results of trend analyses for four sub-regions. Results for Bicknell’s Thrush, Winter Wren and Whitethroated Sparrow results are from 2003-2006. Results for Blackpoll Warbler, Fox Sparrow and Swainson’s Thrush
are from 2002-2006. r is the instantaneous rate of change. Significant rates of change (P<0.05) are highlighted in
grey. Significant differences in trends were determined using ANCOVA.
North-western New Brunswick
SE(r)
0.035
0.026
0.032
%annual
change
-9.1
-1.8
-5
SE(%)
3.2
2.6
3.1
0.036
0.045
1.4
13.4
0.052
r
-0.059
0.067
0.031
Sig diff in
trends
between
NW and NCentral NB
Sig diff in
trends
between
Park and
Outside
r
-0.145
-0.041
-0.055
SE(r)
0.041
0.037
0.037
%annual
change
-13.5
-4
-5.3
SE(%)
3.6
3.5
3.5
*
*
3.7
5.1
-0.062
-0.074
0.05
0.033
-6
-7.1
4.7
3
*
*
-9.5
4.7
SE(r)
0.026
0.019
0.023
%annual
change
-5.7
6.9
3.2
SE(%)
2.4
2
2.4
-0.089
0.071
-8.5
6.5
Nova Scotia Outside Cape Breton Highlands Nat Park
%annual
r
SE(r)
change
SE(%)
-0.068
0.031
-6.5
2.9
0.101
0.028
10.7
3.1
*
0.088
0.029
9.2
3.1
*
0.034
0.058
0.026
0.033
3.4
5.9
2.7
3.5
0.114
0.018
0.039
0.024
12
1.8
4.3
2.5
-0.08
0.038
-7.7
3.5
-0.07
0.053
-6.8
4.9
Species
r
-0.096
Bicknell’s Thrush
Blackpoll Warbler -0.018
Fox Sparrow
-0.051
Swainson’s
0.014
Thrush
Winter Wren
0.126
White-throated
Sparrow
-0.099
North-central New Brunswick
Bicknell’s Thrush
Blackpoll Warbler
Fox Sparrow
Swainson’s
Thrush
Winter Wren
White-throated
Sparrow
Nova Scotia Cape Breton Highlands National Park
*
*
*
*
*
*
3. Trends in number of stops occupied by Bicknell’s Thrush
Analyses of the number of stops at which Bicknell’s Thrush were detected annually from 20032006 showed significant declines (P<0.05) in Bicknell’s Thrush for all four sub-regions. The
actual rates of decline differed somewhat, with the number of occupied stops within the Park
declining faster than the remainder of Cape Breton and the number of occupied stops in northwestern New Brunswick declining faster than the number in the north-central part of the
province.
Proportion of plots occupied
0.25
0.20
0.15
0.10
0.05
Northwest NB
North-central NB
0.00
2003
2004
2005
2006
Year
Figure 3. Change in number of stops occupied by Bicknell’s Thrush from 2003-2006 in
Northwestern New Brunswick and North-central New Brunswick. The predicted lines are fitted
based on logistic regression.
0.35
Outside Park
Inside Park
Proportion of plots occupied
0.30
0.25
0.20
0.15
0.10
0.05
0.00
2003
2004
2005
2006
Year
Figure 4. Change in number of stops occupied by Bicknell’s Thrush from 2003-2006 on routes
outside of Cape Breton Highlands National Park and routes within Cape Breton Highlands
National Park. The predicted lines are fitted based on logistic regression.
Discussion
Although the High Elevation Landbird Program has existed for only a few years, the results
show significant declines in Bicknell’s Thrush along survey routes using two different analysis
techniques. These declining trends persist over all four sub-regions. Bicknell’s Thrush declines
were particularly severe in 2006, with more than 66% fewer birds detected in New Brunswick
and 87% fewer in Nova Scotia than in 2005. Indeed, 2006 had the lowest number of Bicknell’s
Thrush detected of any survey year to date. It is possible that declines represent the effects of a
very poor year in 2006 rather than an overall decline since the start of the survey. Further surveys
will prove crucial in determining if this is the case.
White-throated Sparrow was the only other species monitored by HELP that also showed
significant declines in both New Brunswick and Nova Scotia, although these trends were no
longer significant when broken down by sub-region, except for north-central New Brunswick.
Data from the Breeding Bird Survey also showed 2% annual declines in White-throated Sparrow
in Nova Scotia and New Brunswick between 1967 and 2005, although only New Brunswick
declines are significant (Canadian Breeding Bird Survey website: http://www.cwsscf.ec.gc.ca/mgbc/trends/index.cfm?lang=e&go=info.birdSummaryProvince&provid=9&speciesi
d=5580).
Pre-commercial thinning is likely to have had a significant impact on breeding habitat in New
Brunswick as 70% of stands in the study area were thinned within the last four years. Precommercial thinning is a silvicultural technique that increases the growth rate of trees by
reducing stem density in regenerating stands or plantations after a clearcut. Stem density can go
from as much as 50,000 stems/ha before pre-commercial thinning to around 5 000 stems/ha (H.
Russel pers. Comm..). Studies have shown declines in Bicknell’s Thrush following precommercial thinning in New Brunswick. (Chisholm 2005, Campbell et al. 2005), although there
is some evidence that habitat for Bicknell’s Thrush may regenerate prior to harvest (Gardiner
2006). Appendix B presents additional information on impacts of thinning in New Brunswick
along three HELP survey routes. It is likely that pre-commercial thinning is having some impact
on breeding abundance of Bicknell’s Thrush in New Brunswick. However, pre-commercial
thinning can not explain the similar decline in Bicknell’s Thrush observed in natural habitat in
Cape Breton Highlands National Park.
It is possible that as habitat quality changed on surveys routes due to the growth of trees and
other vegetation or the thinning of prime habitat, Bicknell’s Thrush selected alternate areas
nearby in which to nest. This would cause decline along HELP routes that may not translate to a
real decline across the species’ Maritime range. However, in 2006, HELP surveyors also
conducted many point counts in nearby areas during the same survey period, as part of the
Maritimes Breeding Bird Atlas initiative. In New Brunswick, although approximately 80 point
counts were conducted in potential Bicknell’s Thrush nesting habitat, no individual Bicknell’s
Thrush were recorded. Although similar data from Cape Breton have not yet been compiled, no
Bicknell’s Thrush were detected on any of the 2006 point counts conducted in the Maritimes
which have been entered into the Breeding Bird Atlas database to date. The lack of records in
nearby Atlas squares provides corroborative evidence that declines may be real, rather than a
shift to other nearby nesting locations as habitat along survey routes changed.
Analyses of data from the White Mountains of New Hampshire showed significant declines in
Bicknell’s Thrush from 1993-2003 (D. King in review). Furthermore, data from the High
Elevation Landbird Program’s sister program in the U.S., Mountain BirdWatch, run by the
Vermont Institute of Natural Science (VINS), also estimated a 9% annual decline in Bicknell’s
Thrush in New England from 2001 to 2004 (Lambert 2005). However, in 2005 and 2006 there
was a reversal of this continuing decline, and in 2006 VINS recorded the highest relative
abundance of Bicknell’s Thrush since their program began in 2001 (Lambert 2007).
Additionally, banding data examining changes in capture rates between early years (1970-85)
and late years (1986-2001) show significant declines in Gray-cheeked/Bicknell’s Thrush during
both spring and fall migration periods at Manomet Center for Conservation Sciences in
Massachusetts (Lloyd-Evans and Atwood 2004), although the lack of ability to distinguish Graycheeked and Bicknell’s Thrush (due to the relatively recent designation of Bicknell’s Thrush as a
separate species from Gray-cheeked Thrush, in 1995; Ouellet 1993) in this analysis makes these
data of less direct value.
Nixon et al. (2001) estimated an average density of 16 pairs/100 ha (range of 3 to 22 pairs/100
ha) in 1997 after conducting fieldwork in north-central New Brunswick. Using their method of
calculating density, HELP results show an average density of 11.4 pairs/100 ha in 2003,
declining to 2.23 pairs/100 ha in 2006, suggesting that the decline may have been ongoing for
some time.
The fact that Bicknell’s Thrush declines in the Maritimes appear to be occurring in both natural
and industrial areas, in geographically disparate areas, and in New England where declines
cannot be attributed to forestry (little or no logging is undertaken in the regions studied) suggest
that factors other than, or in addition to, forestry are responsible for the observed declines. Acid
rain, mercury deposition (Rimmer et al. 2005), climate change (Lambert et al. 2005) and habitat
loss in wintering grounds (Latta et al. 2003) are all possible contributors to a global population
decline throughout the range of Bicknell’s Thrush.
It can be difficult to interpret the short-term results from just four years of HELP surveys. Many
years of monitoring may be necessary to observe effects of habitat change, climate change, acid
rain and mercury deposition on bird populations. However, strong, short-term trends may
provide an early warning of serious population decline. It is therefore important to begin
mitigation measures early, before a more reliable description of population change is available,
at which point it may be too late to save a species reduced to drastically low population levels
and in continuing decline.
We would like to make the following recommendations for further work on Bicknell’s Thrush in
Maritime Canada:
-
Fieldwork for the Maritimes Breeding Bird Atlas will continue through to 2010. This
project will map the distribution and abundance of all birds throughout the Maritime
Provinces. This will allow us to compare the present distribution and abundance of
Bicknell’s Thrush with those observed from 20 years ago (Erskine 1992). Atlas results, in
combination with continued annual HELP surveys, should provide us with a clearer
picture of population trends within the next five years. Continued monitoring through
both Atlas surveys in areas of potential Bicknell’s Thrush habitat, and HELP surveys,
should be given priority in planning future action for Bicknell’s Thrush conservation.
-
An International Bicknell’s Thrush working group should be convened to facilitate timely
and thorough information sharing on Bicknell’s Thrush status, trends and innovations in
data analysis and research in the U.S. and Canada and on the species Hispaniola
wintering grounds. While an official working group has not yet been created, a first
meeting of International partners has been set for May 4, 2007 with participants meeting
by teleconference from two main nodes: Sackville, New Brunswick (Canadian Wildlife
Service and Bird Studies Canada) and Quechee, Vermont (Vermont Institute of Natural
Science).
-
Analyses should be conducted to examine whether, and to what degree, HELP routes are
representative of available Bicknell’s Thrush habitat in Maritime Canada. Routes were
selected randomly using somewhat different procedures in New Brunswick and Nova
Scotia (see Whittam 2002); however they may not be fully representative of all habitat
types used by Bicknell’s Thrush in the region. Furthermore, rapid changes in habitat
along routes in industrial forest no doubt impact the use of this habitat by Bicknell’s
Thrush; however, no monitoring method has been discussed to account for this change.
Floating routes, or a greater number of routes in a larger variety of stand ages, may be
required.
-
Analyses should be conducted to determine and account for variation in detectability of
Bicknell’s Thrush along HELP survey routes. Detectability of Bicknell’s Thrush tends to
be low in New Brunswick (40% chance of detection with one visit), and six or more
visits appear to be needed to detect all birds at a given site (Nixon et al. 2001). We have
not examined detectability of Bicknell’s Thrush along HELP routes in either New
Brunswick or Nova Scotia; however, given that we note bird detections on a minute-byminute basis for the entire 10-minute silent listening period, a site occupancy analysis
should be possible (Mackenzie et al. 2002). Preliminary results from Quebec suggest that
two five-minute passive listening periods detect 77-78% of birds present; however
detectability may vary with geographic location (Y. Aubry and M. Mazerolle unpubl.
data). Detectability should be considered in a monitoring program, especially if it does
not remain constant over time (Martin et al. 2007).
-
Research on impacts of pre-commercial thinning on Bicknell’s Thrush in New Brunswick
(Chisholm 2005; Gardiner 2006) should continue with support and participation by Bird
Studies Canada as appropriate.
Acknowledgements
Funding for this project in 2006 was provided by the Government of Canada Habitat
Stewardship Program for Species At Risk, the Canadian Wildlife Service, the Shell
Environmental Fund, and UPM-Kymmene. In past years funding was also provided by Parks
Canada, Canadian Forest Service, Science Horizons Youth Internship Program, Endangered
Species Recovery Fund of World Wildlife Fund and Environment Canada, NB Student
Employment and Experience Development (SEED) program, Human Resources Development
Canada and Stora Enso Port Hawkesbury. Special thanks to the Maritimes Breeding Bird Atlas
for sharing staff and equipment. Further in-kind support was provided in 2006 by Parks Canada,
Fraser Papers Inc., Stora Enso Port Hawkesbury Ltd. and the New Brunswick Department of
Natural Resources. Thanks to Kate Bredin for reviewing an earlier draft of this manuscript and
to Richard Elliot for providing some text related to population trends.
A very heartfelt thank you to our dedicated volunteers: Jim Clifford, Tim Courage, Roy
LaPointe, Roger LeBlanc and Mike Lushington Thanks to our 2006 field crew: Emily
McKinnon, Steve Gullage and Josh Pennell. Cathleen Gallant entered the 2006 data.
References
Campbell, G., B. Whittam and S. Chisholm. 2005. Bicknell’s Thrush in New Brunswick Forests:
What we know, what we need to know, and how the forestry industry can help.
Unpublished report, Bird Studies Canada, Sackville, NB.
Chisholm, S.E. 2005. The impact of precommercial thinning on abundance of Bicknell’s Thrush
and other high elevation birds. M.Sc. Thesis, Dalhousie University, Halifax, Nova Scotia,
Canada.
Connolly, V., G. Seutin, J-P. L. Savard and G. Rompré. 2002. Habitat use by the Bicknell’s
Thrush in the Estrie region, Quebec. Wilson Bulletin 114: 333-341.
Erskine, A. J. 1992. Atlas of breeding birds of the Maritime provinces. The Nova Scotia Museum
and Nimbus Publishing, Halifax, NS. 270 pp.
Gardiner, R.J. 2006. The long-term effects of pre-commercial thinning on Bicknell’s Thrushes
and four other high elevation songbirds in the New Brunswick highlands. B.Sc. Thesis,
Mount Allison University, Sackville, NB, Canada.
Hart, R., and C. Carroll. 2004. High Elevation Landbird Program, 2003 Report. Unpublished
Report by Bird Studies Canada (Atlantic Region), Sackville, NB.
www.bsc-eoc.org/regional/acbithsurvey.html
King, D.I., D. King, J.D. Lambert, J. P. Buonaccorsi, L. S. Prout. In review. Avian population
declines in montane spruce-fir forests of the northern Appalachians, USA.
Lambert, J.D. 2003. Mountain Birdwatch 2002. Final Report To The United States Fish And
Wildlife Service by the Vermont Institute of Natural Science.
www.vinsweb.org/cbd/2003_Report.html
Latta, S. C., C. C. Rimmer and K. P. McFarland. 2003. Winter bird communities in four habitats
along an elevational gradient on Hispaniola. Condor 105: 179-197.
Lambert, J.D. 2005. Mountain Birdwatch 2004. Final Report To The United States Fish And
Wildlife Service by the Vermont Institude of Natural Science.
www.vinsweb.org/cbd/2004_Report.html
Lambert, J.D. 2006. Mountain Birdwatch 2005. Final Report To The United States Fish And
Wildlife Service by the Vermont Institute of Natural Science. VINS Technical Report 06-2.
Lambert, J.D., K. P. McFarland, C. C. Rimmer, S. D. Faccio and J. L. Atwood. 2005. A practical
model of Bicknell’s Thrush distribution in the northeastern United States. Wilson Bulletin
117: 1-11.
Lloyd-Evans, T.L. and J. L. Atwood. 2004. 32 years of changes in passerine numbers during
spring and fall migrations in coastal Massachusetts. Wilson Bulletin 116:1-16.
MacKenzie, D. I., J. D. Nichols, G. B. Lachman, S. Droege, J. A. Royle, and C. A. Langtimm.
2002. Estimating site occupancy rates when detection probabilities are less than one.
Ecology 83:2248-2255.
Martin, J., W. M. Kitchens and J. E. Hines. 2007. Importance of well-designed monitoring
programs for the conservation of endangered species: case study of the Snail Kite.
Conservation Biology 21:472-481.
Nixon, E.A., S.B. Holmes and A.W. Diamond. 2001. Bicknell’s Thrushes (Catharus bicknelli) in
New Brunswick clear cuts: their habitat associations and co-occurrence with Swainson’s
Thrushes (Catharus ustulatus). Wilson Bulletin 113: 33-40.
Ouellet, H. 1993. Bicknell’s Thrush: taxonomic status and distribution. Wilson Bulletin 105:
545- 572.
Rimmer, C.G., K.P. McFarland, W.G. Ellison and J.E. Goetz. 2001. Bicknell’s Thrush (Catharus
bicknelli). In The Birds of North America, No. 592 (A. Poole and F. Gill, eds.). The Birds
of North America, Inc., Philadelphia, PA.
Rimmer, C.G., K.P. McFarland, D.C. Evers, E.K. Miller, Y. Aubry, D. Busby and R.J. Taylor.
2005. Mercury concentrations in Bicknell’s Thrush and other insectivorous passerines in
montane forests of northeastern North America. Ecotoxicology 14: 223-240.
Stattersfield, A.J., and D.R. Capper. 2000. Threatened birds of the world: the official source for
birds on the IUCN red list. Cambridge: BirdLife International.
Appendix A – Five year trends for Bicknell’s Thrush using partial HELP data set
The High Elevation Landbird Program (HELP) started in 2002, with the original protocol
including 30 seconds of Bicknell’s Thrush playback in the middle of the 10 minutes of silent
listening. This 30 second playback was removed in 2003 in order to harmonize methods with the
Vermont Institute of Natural Science’s Mountain Birdwatch program (Hart and Carroll, 2004).
To examine five-year trends for Bicknell’s Thrush, we compared the first five minutes of survey
results in 2002 to the first five minutes of results from 2003-2006 using the same analysis
techniques described in the methods section of the main report. Because the detectability of
Bicknell’s Thrush is much lower with only five minutes of silent listening compared with 10
minutes (Y. Aubry unpubl. data) we decided to present the four-years of data including the full
10 minute protocol in the main document, and the five-years of data with the five minute
protocol in this appendix.
When 2002 data are included by using only the first five minutes of the HELP protocol, some of
the significant results are no longer apparent; this is generally due to 2002 have slightly lower
numbers than 2003 and 2004. The decline in northwestern New Brunswick (Table A1) is
marginal (P = 0.085) and the decline in Nova Scotia outside the Park is no longer significant.
However there were very few detections of Bicknell’s Thrush outside the Park to start with,
making it more difficult to show declines even if they exist. The occupancy analysis (Figures
A1-3) showed similar, albeit somewhat stronger trends, as only outside the Park in Nova Scotia
is not showing a significant reduction in occupancy.
Overall, the general patterns seen in the four year data set seem to also appear in the five year
partial data set, although the magnitude is somewhat diminished in some of the regions, due to
2002 usually being a 'middle' year. Regardless, 2006 is the lowest year on record for all metrics.
Whether these trends represent a general decline, or a 2006 effect, is debatable, as only
sometimes, but not always, is 2005 the second lowest year. Continued surveys are necessary to
determine if the declining trend will continue.
Table A1. Results of trend analyses for Bicknell’s Thrush from 2002-2006 using only the first five minutes of
HELP surveys. Results are listed by province and then by sub-regions within the two provinces. r is the
instantaneous rate of change. Significant rates of change (P<0.05) are highlighted in grey. There were no significant
differences between trends within Nova Scotia (Park vs outside park) or within New Brunswick (North-central vs
northwestern).
New Brunswick All
Bicknell’s
Thrush
Nova Scotia All
r
SE(r)
%annual
change
-0.059
0.014
-5.8
SE(%)
r
SE(r)
%annual
change
SE(%)
1.3
-0.044
0.015
-4.3
1.4
r
SE(r)
%annual
change
SE(%)
Nova Scotia Cape Breton Highlands
National Park
%annual
r
SE(r)
SE(%)
change
-0.044
0.024
-4.3
2.3
-0.077
North-western New Brunswick
Bicknell’s
Thrush
-7.4
2.3
r
SE(r)
%annual
change
SE(%)
Nova Scotia Outside Cape Breton
Highlands National Park
%annual
r
SE(r)
change
SE(%)
-0.066
0.017
-6.3
1.6
-0.018
North-central New Brunswick
Bicknell’s
Thrush
0.025
0.019
-1.8
1.9
0.25
Proportion of plots occupied
Nova Scotia
New Brunswick
0.20
0.15
0.10
0.05
0.00
2002
2003
2004
2005
2006
Year
Figure A1. Change in number of stops occupied by Bicknell’s Thrush from 2002-2006 in Nova
Scotia and New Brunswick, using first five minutes of HELP survey. The predicted lines are
fitted based on logistic regression. Both declines are significant (P<0.05).
0.30
Outside Park
Inside Park
Proportion of plots occupied
0.25
0.20
0.15
0.10
0.05
0.00
2002
2003
2004
2005
2006
Year
Figure A2. Change in number of stops occupied by Bicknell’s Thrush from 2002-2006 on routes
outside of Cape Breton Highlands National Park and routes within Cape Breton Highlands
National Park, using first five minutes of HELP survey. The predicted lines are fitted based on
logistic regression. Only the decline within the Park is significant (P<0.05).
0.30
NW NB
Central NB
Proportion of plots occupied
0.25
0.20
0.15
0.10
0.05
0.00
2002
2003
2004
2005
2006
Year
Figure A3. Change in number of stops occupied by Bicknell’s Thrush from 2002-2006 in
Northwestern NB and North-central NB, using first five minutes of HELP survey. The predicted
lines are fitted based on logistic regression. Both declines are significant (P<0.05).
Appendix B – Results for three routes examined pre- and post-thinning in New Brunswick
In 2003, 2004 and 2005 Chisholm (2005) and Gardiner (2006) examined impacts of precommercial thinning in north-central New Brunswick on UPM Kymmene’s crown lease by
counting abundance of Bicknell’s Thrush along three routes in the year before thinning (2003)
and the two years following thinning (2004, 2005). They ran each route four times and averaged
the abundance annually. In 2006 there was no graduate or honour’s student assigned to this
project so HELP staff re-ran these three routes. Unfortunately there was not time to run these
routes more than once given other HELP duties. Figure B1 shows abundance of Bicknell’s
Thrush on the first run of each of these three routes from 2003 to 2006. It is worth noting that
along two of these three routes the Bicknell’s Thrushes that were detected in the years postthinning were heard singing or calling from patches of unthinned habitat within the (mostly
thinned) stand.
Average number of Bicknell's Thrush detected
7
6
5
4
3
2
1
0
2003 pre-thin
2004 - 1 yr post-thin
2005 - 2 yr post-thin
2006 - 3 yr post-thin
Figure B1. Average number of Bicknell’s Thrush detected (±SE) along three routes in northcentral New Brunswick from pre-thinning (2003) to three years post-thinning (2006).