Supplement

Published

June 30, 2025

S1 Measurement error

Longitudinal (blue) and latitudinal (orange) measurement errors, which are used in the observation model part of the HMM, vary depending on the antenna orientation up to half of the theoretical antenna detection range. Note that this figure illustrates measurement errors specifically for a 6-element Yagi antenna.

S2 Test flight GPS track

Altitude

GPS track of the test flight. Colours correspond to altitude in m (hover for info).

Histogram of GPS track altitudes in m.

Speed

GPS track of the test flight. Colours correspond to speed in ms-1 (hover for info).

Histogram of GPS track speeds in ms-1.

Distance travelled between signal bursts

Note

Assume reasonable airspeeds of songbirds to be \(\text{Log-Normal}(\log(12), 0.2)\) ms-1.

Distance travelled between signal bursts for the airspeed of the test plane and a reasonable airspeed of a songbird.

S3 Receiver network

Map of the receiver network during the test flight. Mean antenna beams are shown for each bearing, with a range of 10 km. Antennas displayed in red were nonfunctional.

S4 Detections by Motus

Number of detections

Note

The maximum timestamp difference between a Motus detection and a GPS fix is 6.3 s.

tagDeployID date burst interval [s] n
56173 2024-07-09 7.1 1364
56174 2024-07-09 7.3 1360
56175 2024-07-09 29.3 30
56176 2024-07-09 29.3 18
56178 2024-07-09 19.1 132
56825 2024-07-11 7.1 1032
56826 2024-07-11 7.3 1702
56827 2024-07-11 29.3 82
56828 2024-07-11 29.3 70
56830 2024-07-11 19.1 114

Number of synchronous detections

Number of synchronously receiving Motus antennas.

Positions with detections by Motus

GPS track of the test flight. Motus receivers with detections are shown in black, blue circles indicate GPS fixes with detections by Motus receiver.

S5 Compare tracks

Note
  • dTime is the time interval in minutes for which point estimates are calculated.
  • aRange is the assumed maximum detection range of antennas in km.
  • Unless otherwise specified, the number of states used in the model is 2.

Burst interval 7.3

Number of states

The ‘best’ estimated flight track using different numbers of states together with GPS track of the test flight indicating GPS fixes with detections by Motus receiver.

Burst interval 19.1

Burst interval 29.3

S6 Best estimate

Note

Parameter values used in this section: tagBI = 7.3 s, dTime = 0.5 min, aRange = 10 km and states = 2.

The ‘best’ estimated flight track together with GPS track of the test flight indicating GPS fixes with detections by Motus receiver.