Table 4.

Methods used to derive incubation in biparental shorebirds.

methoda	How was incubation derived?	sampling interval (min)	N populations	N nests
RFID with temperature probe between the eggs	a thin antenna loop, placed around the nest cup and connected to the reader, registered presence of tagged parents at the nest; the passive-integrated tag was either embedded in a plastic flag [12] with which the parents were banded, or glued to the tail feathers [44]. Temperature recordings allowed to identify whether a bird was incubating even in the absence of RFID readings; an abrupt change in temperature demarcated the start or end of incubation [12]	0.08–5.5	23	200
light logger attached to bird's leg	the logger recorded maximum light intensity for a fixed sampling interval (2–10 min) and recorded darkness when parent was incubating. An abrupt change in light intensity (as opposed to a gradual change caused, e.g. by civil twilight) followed by a period of low or high light intensity demarcated the start or end of the incubation period [11]	2–10	71	396
GPS tag mounted on the back of the bird	the tag recorded the position of the bird [45] and incubation was assumed whenever the bird was within 25 m of the nest	10–30	2	9
automated receivers	receivers recorded signal strength of a radio-tag attached to the rump of a bird; whenever a bird incubated, the strength of the signal remained constant [10]	0.07	2	3
video cameras and continuous observations	videos and observations were used to identify the incubating parents; parent identification was based on plumage, colour rings or radio-tag	constant - 30	6	61

^aFor technical specifications of the methods, see Extended Data table 1 in [11].