06 February 2010

Nest Scrape Characteristics of Piping Plover and Least Tern in Nebraska

A previous article talked about the nest features of tern and plovers on the Missouri River. This is an evaluation of particulars, and though the text is old-time history, this is the first time for showing the pictures. Obvious differences are visible that indicate particulars of discoveries during breeding bird surveys.

The Belted Piping Plover (Charadrius melodus circumcinctus) and Interior Least Tern (Sterna antillarium athalassos) are uncommon local breeders on the Missouri, Platte, Middle Loup, and Niobrara rivers in Nebraska. Both of these species scrape their nests in the sand substrate found on riverine sandbars and sandpits. The Plover and Tern are often associated with one another in these habitats.

During the years 1981 to 1983, while I was collecting information on species occurrence and populations, primarily of the Least Tern, I also collected data on the characteristics of nest scrapes used by both species.

A comparison to determine any differences was based on an analysis of scrape contents and of a 1 meter diameter circle surrounding the nest. The presence or absence of vegetation, whether or not there was an association with some type of debris, and the presence or absence of fragments within the scrape were recorded. Other characteristics recorded were the height and species of vegetation present during the months of June or July, the type of debris and scrape fragments, or type of nest lining. Data were separated into a specific group within each of the three categories measured.

Vegetation was identified according to the plant type, such as grass, willow, or cattail. Debris associated with the nest was considered either woody or plant material. Fragments within the scrape were either pebbles; twiglets, which were little pieces of twigs; or shreds of plant material.

If one of the three features measured was observed, it was then placed into one of six percent cover categories, based on the relative amount of area covered within the circle or scrape (Table 1).

Results

Piping Plover

Of 142 scrape analyzed for vegetation, 99, or 70%, had no vegetation, and 43, or 30%, had vegetation present. Vegetative cover was sparse, with values ranging from 2.5% to 37.5% (Table 1). Seven plant types were recorded, with cattail, willow and bulrush the most common. Cattail was the tallest plant present (Table 2). The plant types present at the different scrapes have a total greater than the overall number of scrapes with vegetation, since more than one plant could have been noted in the vicinity of a particular nest. Each nest could then have more than one separate listing for plant types. An example of a combination would be both cattail and willows, which was recorded at five scrapes.

Table 1. Percent cover of selected characteristics of nest scrapes.

Cover

Range

Vegetation Present

Debris Association

Scrape Fragments

Plover

Tern

Plover

Tern

Plover

Tern

Category

From

To

#

%

#

%

#

%

#

%

#

%

#

%

2.5%

1%

5%

26

18

28

24

66

44

40

30

22

17

9

8

15.0

5

15

14

10

8

7

14

9

30

23

13

10

4

4

37.5

25

50

3

2

-

-

-

-

1

1

19

14

3

3

62.5

50

75

-

-

-

-

-

-

-

-

14

11

-

-

85.0

75

95

-

-

-

-

1

1

-

-

31

23

-

-

98.5

95

100

-

-

-

-

-

-

-

-

-

-

-

-

No detail

-

-

-

-

47

32

24

18

-

-

-

-

Some cover

43

30

36

31

128

86

95

72

105

79

16

15

No cover

99

70

80

69

21

14

37

28

28

21

93

85

Total

142

100

116

100

149

100

132

100

133

100

109

100

No scrape debris was recorded at 21, or 14%, of the 149 scrapes analyzed, with 128, or 86%, having this feature. Percent cover was usually low, but one unusual site had a value of 85%, which was a scrape almost entirely covered by an 18 cm. log 8 cm. over the nest (Table 1). Most of the debris was woody material (Table 3).

Piping Plover nest on the Platte, July 1980.

Piping Plover nest, summer 1981.

Table 2. Summary of plant types and height of vegetation at nest scrapes.

 

Piping Plover

Least Tern

Vegetation Type

Number of Sites

%

Plant Height (cm.)

Number of Sites

%

Plant Height (cm.)

Range

Average

Range

Average

Grass

2

3

-

-

2

4

-

-

Cattail

18

26

30-100

71

4

9

30-70

55

Willow

16

24

20-100

40

11

24

10-30

35

Bulrush

16

24

20-110

54

11

24

10-80

35

Sedge

8

12

20-40

22

6

13

10-30

17

Cottonwood

7

10

10-40

21

4

9

10-20

16

Clover

1

1

20

20

-

-

1

-

Equisetum

-

-

-

-

2

4

10

10

Succulent

-

-

-

-

6

13

5

5

Total

68

100

 

 

46

100

 

 

Observations of fragment contents were made at 133 nests, with 28 or 21%, not having any present, and 105, or 79%, that had variable amounts of fragments lining the scrape (Table 1). Pebbles occurred with the greatest frequency (Table 4).

Piping Plover nest with eggs, June 1981.

Piping Plover nest site, summer 1982.

Least Tern

Of the 116 nests where the vegetation was analyzed, 80, or 69%, had none present, while 36, o 31%, had plant growth (Table 1). Willow and bulrush were most common, with cattail the tallest plant (Table 2).

Debris occurrence at 132 nests showed 37, or 28%, were not associated with any debris, and 95, or 72%, which mostly had 2.5% or 15% debris cover within the one meter circle around the nest (Table 1). Woody material was most prevalent (Table 3).

Table 3. Type of debris material associated with nest scrapes.

Type of debris

Plover

Tern

#

%

#

%

Woody material

 

56

 

71

Stick

37

41

31

43

Driftwood

34

38

19

26

Twig

7

8

5

7

Bark

8

9

15

21

Burnt wood

4

4

2

3

Total woody material

90

100

72

100

Plant material

 

42

 

29

Root

9

20

6

21

Dried bulrush

25

56

18

62

Grass

1

2

3

10

Dried cattail

2

4

2

7

Dried sedge

3

7

-

-

Cornstalk

2

4

-

-

Unidentified

3

7

-

-

Total plant material

45

100

29

100

Rock, cow vertebra

2

2

-

-

Grand total

137

100

101

100

Fragments within the scrape were not present at 93, or 85%, of 109 nests analyzed (Table 1), with 16, or 15%, having from 2.5% to 37.5% cover (Table 1). Pebbles and twiglets had a similar occurrence (Table 4).

Table 4. Type of fragment found in nest scrapes.

Type of fragment

Plover

Tern

#

%

#

%

Pebbles

97

90

8

50

Twiglets

7

6

7

44

Rootlets

-

-

1

6

Bark flakes

3

3

-

-

Plant fibers

1

1

-

-

Total

108

100

16

100

Comparison

Differences between species were apparent in two of the categories measured. A one-way analysis of variance was used to determine any statistical difference between the values recorded. Piping Plover had greater percent plant cover with a significant difference (p less than 0.05) between the two species.

Differences in the amount of fragments lining the scrape were very apparent. Piping Plover had a greater percent occurrence of fragments than the Least Tern. Values were 79% versus 15%, respectively. There was also a highly significant difference (p less than 0.01) in the amount of fragment cover within the nest. The Plover had a greater amount of fragments present, with values reaching 100% cover, and pebbles most prevalent. Terns had about the same frequency of either pebbles or twiglets.

Least Tern nestling and egg during summer of a Nebraska river.

Originally published in 1988 as: Nest scrape characteristics of the Piping Plover and Least Tern in Nebraska. Nebraska Bird Review 56: 42-44.

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