Recording long-term field observations of organisms can be helpful in determining the abundance and diversity

Recording long-term field observations of organisms can be helpful in determining the abundance and diversity

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BIRD MONITORING TRENDS FROM DATA COLLECTED BY SUE SHAW Analysis and Report by Susie Fork, January 2002 The information gathered by counting the numbers and kinds of animals found in a particular ecosystem can tell us much about the value of these areas to animals, and changes in abundance and diversity of particular groups of animals may also reflect underlying changes in the habitat. Birds are ideal for studies of wetlands, because they are often present in great numbers here, and many are easily identified from a distance. Important measures include overall bird diversity and abundance of the entire study area, as well as comparisons of different sites within the area. While faithfully carrying out water monitoring, volunteer Sue Shaw decided also to take on the challenge of keeping detailed notes of the abundance and diversity of birds she saw at each of the of 26 sites during 1989-2000. Stations were located the along entire length of the slough from the mouth at Moss Landing and adjacent areas all way up to the head of the slough. Additionally, Sue also monitored stations further south at Salinas River, Moro Cojo, and nearby locations. In all, 29 different types of birds were recorded at Elkhorn Slough and environs. More commonly seen birds included loons, cormorants, pelicans, gulls, terns, shorebirds, herons, egrets, ducks, geese, coots, grebes, and kingfishers. The total abundance of birds counted at Elkhorn Slough and ...

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BIRD MONITORING TRENDS FROM DATA COLLECTED BY SUE SHAW
Analysis and Report by Susie Fork, January 2002
The information gathered by counting the numbers and kinds of animals found in a particular
ecosystem can tell us much about the value of these areas to animals, and changes in abundance and
diversity of particular groups of animals may also reflect underlying changes in the habitat. Birds
are ideal for studies of wetlands, because they are often present in great numbers here, and many are
easily identified from a distance. Important measures include overall bird diversity and abundance
of the entire study area, as well as comparisons of different sites within the area.
While faithfully carrying out water monitoring, volunteer Sue Shaw decided also to take on the
challenge of keeping detailed notes of the abundance and diversity of birds she saw at each of the of
26 sites during 1989-2000. Stations were located the along entire length of the slough from the
mouth at Moss Landing and adjacent areas all way up to the head of the slough. Additionally, Sue
also monitored stations further south at Salinas River, Moro Cojo, and nearby locations. In all, 29
different types of birds were recorded at Elkhorn Slough and environs. More commonly seen birds
included loons, cormorants, pelicans, gulls, terns, shorebirds, herons, egrets, ducks, geese, coots,
grebes, and kingfishers.
The total abundance of birds counted at Elkhorn Slough and adjacent areas did not change over
the 8-year period (for statistical reasons, only data from 1992-1999 were analyzed), which is good
news. Abundance of individual bird groups (e.g. gulls, terns, cormorants, Great Blue Herons,
egrets, and geese) also remained unchanged. Two exceptions were coot and loon numbers, which
increased significantly over the 1990s. Others whose abundance increased slightly included
American Avocets, Black-necked Stilts, ducks, geese, and pelicans.
Annual totals of overall bird abundances varied between sites. Salinas River Lagoon took top
honors with a total of nearly 9000 birds, most of which were gulls (7000) and pelicans (800)! The
remaining included terns and cormorants, and lesser numbers of shorebirds, grebes and coots. Sites
with the lowest abundances were the Porter marsh side of Hudson Landing, Upper and Lower Pond
at Azevedo Ranch, and Moss Landing Rd. (less than 50 birds each). Abundance of specific bird
groups also varied significantly between sites for pelicans, loons, ducks, coots, gulls, terns, egrets,
American Avocets, Black-necked Stilts, shorebirds, and Belted Kingfishers. For example, the
highest numbers of ducks (> 200 birds) were observed at Skippers, while coots were most abundant
at North Marsh at Strawberry Rd. and Moro Cojo (> 100 at each site). Shorebirds numbers were
highest at Strawberry (>400), Jetty Rd. (200), Kirby Park and the railroad side of Hudson’s Landing
(>100 at each site). Waders (herons, egrets, avocets and stilts) were most abundant at Strawberry
(North Marsh) and North Potrero (>50 birds at each site). Of the waders, the egrets were found
mostly at Jetty Rd. and Reserve Bridge (15-20 birds at each site). Over the years several Belted
Kingfishers were consistently observed at South Marsh and East Bennett Slough.
Bird diversity, like bird abundance, also varied significantly between the sites. The sites with the
highest diversity were Jetty Rd. and North Potrero, each supporting more than 12 types of birds
(including loons, cormorants, pelicans, gulls, terns, shorebirds, herons, egrets, ducks, geese, coots,
grebes, and kingfishers). At the other extreme, Carneros Creek Rd. and Monterey Dunes Way each
had fewer than four bird types. Total bird diversity also varied significantly over the years. The
highest diversity of birds was counted from 1996 to 1998, while the lowest diversity was observed
in 1992.
So the good news is that it appears that bird numbers have been stable over the last decade and
diversity may even be increasing. The time and dedication of the volunteers at Elkhorn Slough
towards monitoring projects such as bird censusing are a valuable contribution to our understanding
of this rich and diverse habitat.
FIGURE 1. SAMPLING STATIONS FOR VOLUNTEER WATER QUALITY MONITORING.
0
200
400
600
800
1000
1992
1993
1994
1995
1996
1997
1998
1999
Fig. 2. Total Abundance of Birds vs. Year.
Abundance was steady over time (ANOVA, P=0.93).
0
10
20
30
40
50
60
1992
1993
1994
1995
1996
1997
1998
1999
Fig. 3. Coot Abundance vs Year.
Abundance increased from 1992 – 1999 (ANOVA P=0.03).
0
200
400
600
800
1000
1200
1400
1600
1800
BackBennett
Cameros
EastBennett
HudLdgLP
HudLdgRC
Jetty
Kirby
LowerPond
MidPond
MLRdS
MLRdN
MontDuneWy
MoroCojo
NPotrero
NMarsh
NPotrero
ResBr
SPotrero
SMarsh
SalRvrBr
SalRvrLgn
Skippers
Strawberry
StruvePond
Tembladero
UpperPond
Fig. 4. Total Annual (Mean) Bird Abundance vs. Site.
Mean abundance differed by site (ANOVA P<0.0001) with the highest numbers at Salinas River
Lagoon (nearly 9000 birds).
0
50
100
150
200
250
BackBennett
Cameros
EastBennett
HudLdgLP
HudLdgRC
Jetty
Kirby
LowerPond
MidPond
MLRdS
MLRdN
MontDuneWy
MoroCojo
NPotrero
NMarsh
NPotrero
ResBr
SPotrero
SMarsh
SalRvrBr
SalRvrLgn
Skippers
Strawberry
StruvePond
Tembladero
UpperPond
Fig. 5. Total Annual (Mean) Scolopacidae (willets, godwits, Sanderlings, sandpipers) Abundance
vs. Site.
Number of shorebirds varied between sites (ANOVA P=.04). Strawberry had the highest count with
over 400 birds.
0
50
100
150
200
250
300
BackBennett
Cameros
EastBennett
HudLdgLP
HudLdgRC
Jetty
Kirby
LowerPond
MidPond
MLRdS
MLRdN
MontDuneWy
MoroCojo
NPotrero
NMarsh
NPotrero
ResBr
SPotrero
SMarsh
SalRvrBr
SalRvrLgn
Skippers
Strawberry
StruvePond
Tembladero
UpperPond
Fig. 6. Total Annual (Mean) Waterfowl (Ducks and Geese) Abundance vs. Site.
Number of birds varied between sites (ANOVA P=.04) with the highest numbers at Skippers
(nearly 250 birds).
0
2
4
6
8
10
12
14
16
BackBennett
Cameros
EastBennett
HudLdgLP
HudLdgRC
Jetty
Kirby
LowerPond
MidPond M
LRdS
MLRdN
MontDuneWy
MoroCojo N
Potrero
NMarsh
NPotrero
ResBr
SPotrero
SMarsh
SalRvrBr
SalRvrLgn
Skippers
Strawberry
StruvePond
Tembladero
UpperPond
Fig. 7. Total Annual (Mean) Diversity vs. Site.
Number of birds varied between sites (ANOVA P<.0001) with the highest numbers at Strawberry,
North Potrero, and Jetty
(12 types of birds at each site).
0
1
2
3
4
5
6
7
8
9
10
1992
1993
1994
1995
1996
1997
1998
1999
Fig. 8. Total Annual (Mean) Diversity Over Time.
The diversity of birds was higher in the late vs the early 1990s (ANOVA P<.02).