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.