Camera surveillance in free-range poultry farms

Determination of range usage by hens can be difficult for researchers and free-range egg farmers, particularly usage on the outer sections of the range (i.e., > 50 m from the hen shed). Live counts only give a snapshot of numbers of hens on the range at a defined time point and do not show the frequency of range usage. Camera traps, also referred to as trail cameras and wildlife cameras, are relatively cheap and useful tools that could produce valuable information on the level of range visitation by hens, especially the distant areas on the range. Camera traps have primarily been used for ecological wildlife surveys (e.g. Rovero et al. 2013) and more recently for assessing biosecurity risks on poultry farms by identifying/quantifying the types of wild bird species visiting free-range poultry farms (Scott et al. 2018, Atzeni et al. 2020, Elbers & Gonzales, 2020).

This paper reports on a pilot study that used camera traps to assess the frequency of hens visiting the range areas greater than 50 m (outer range) from the shed on a free-range layer farm in southern Australia. Camera traps were also used to determine the times of the day hens visited the outer range along with hen behaviour and other bird species seen on the range.

Animal ethics approval for the study was from the Department of Primary Industries and Regions, South Australia (PIRSA 13-17). The free-range layer farm was located within the Mediterranean climatic zone of southern Australia. Two flocks (A and B) were studied with camera traps placed on their range areas. The flocks were not adjacent but separated by two other flocks. The hens were Hyline Brown (beak trimmed at hatchery). At the start of camera placement, flock A was 47 weeks of age and flock B was 57 weeks of age. Individual flock sizes on the farm were 30,000 hens with an outdoor stocking density of 10,000 birds/ha.

Sheds (16.5 x 132 m) were orientated East - West with pop holes along both long sides of the shed (north and south facing). The corresponding range area was 4 hectares also orientated East – West in a rectangular shape with the shed located centrally at the Eastern end. Each range area for flocks A and B had four twin rows of oldman saltbush (Atriplex nummularia) variety ‘De Kock’ planted on the range in 2017 and 2018. Rows were 16 m apart commencing 50 m from the western end of the sheds and were 250 m long. Saltbush was arranged in twin rows, 4 m apart, and 4 m separation within rows. Saltbush height ranged from 0.5m to 1 m tall at the time of camera placement.

Cameras (SIGNIFY®, Model Number EA1427, Silverwater, NSW, Australia) with PIR (Passive Infrared) sensors were used. Trigger time was 0.5 sec, trigger distance up to 25 m and the lens with a 100-degree angle. Each camera was loaded with 8 batteries (alkaline AA 1.5v) and a 16 GB SanDisc memory card. Placement of cameras was halfway (8 m from saltbush) between the northern most saltbush twin row and the next saltbush twin row. All cameras were positioned to face south to avoid bright sunrise and sunset effects on the camera lenses. Two cameras were placed on the range of each shed (flocks A and B) at 70 m and 120 m from the west end of the sheds (Total 4 cameras). Cameras were mounted on steel droppers 1m high from the ground using cable ties and were set for medium sensitivity. When triggered, they would take three photographs (5 MB each) in rapid succession followed by a 20-sec video (1280 x 720p).

Photos and videos from three of the four cameras were used. One camera (flock B, 70 m from the west end of shed) had reached storage capacity within 30 days after placement. This was due to excessive bird activity (117 visits by ravens and hens) following the wedge tailed eagle attacks at that location. Therefore, the data from this camera were not included, nevertheless it was used to observe hen behaviour during and following eagle attacks. Hen behaviour was determined from the videos. The following definitions were used; ‘walking’ - to or from the shed with no ground pecking; ‘foraging in open’ - actively pecking and scratching at open ground between saltbush rows; ‘foraging at saltbush’ - pecking and scratching the ground under saltbush; and ‘resting’ - sitting or standing under saltbush without movement. The frequency of hens visiting the area was determined by counting how many times hens appeared during the period the cameras where on the ranges, but only during the times of the day when pop holes were open (10 00 to 18 00 h). Operating time for the cameras was from the 2 August 2019 to 9 October 2019. This covered seasonal weather conditions from late winter to mid spring. A comparison between the number of hens in the photos at 70 m and 120 m was made for flock A using a T-test, unequal variances. Wild bird species were identified from photos and videos. Photos were also used to assess how often hens appeared on the range without wild birds, wild birds without hens, and both hens and wild birds in the same photo. Pearson’s X2 was used to analyse hen behaviour on the range, species of wild birds, and wild birds on the range with and without hens.

The total number of events while popholes were open was N = 102 (based on 3 cameras). False positives represented 11.7 % of the total event numbers. The majority of false positives were on windy days (67%).

At 70 m from the shed, hens from flock A appeared 26 times while at 120 m the hens only appeared 10 times. Yet, there were no significant differences in the average number of hens shown in the photos at 70 m compared to 120 m (3.42 ± 0.81 hens v. 4.37 ± 1.47 hens respectively, P = 0.577, two tailed T-test). Hens ranged away from the shed throughout the day with peak numbers between 10 00 to 11 00 h (shortly after pop holes were opened) (Figure 1). Hens were actively foraging in the open (Frequency = 33), foraging at saltbush (Frequency = 27) or walking on the outer range (Frequency = 23), and resting behaviour was minimal (Frequency = 3) (Pearson’s X2 = 23.58 with 3 d.f., P < 0.001). When resting behaviour was removed from the analysis, the difference between walking and foraging was not significant (Pearson’s X2 = 1.83 with 2 d.f., P = 0.400).

Hens mostly appeared on the range without wild birds (Frequency = 49) (Pearson’s X² = 27.93 with 2 d.f., P < 0.001), followed by wild birds seen without hens (Frequency = 28), and very few occasions where both hens and wild birds were seen in the same photo (Frequency = 9) (except following the eagle attack and these data were not included). The most commonplace wild birds found on the range were Australian ravens (Corvus coronoides), Figure 2, Pearson’s X2 = 80.38, with 6 d.f., P < 0.001. Unidentified birds were the next biggest category. These were small brown birds, half the size of the common starling, probably European house sparrows (Passer domesticus).

The false positives seen on windy days may have been due to moving vegetation triggering camera traps (Rovero et al. 2013). Other false positives may have been the result of fast flying wild birds or insects triggering cameras. There is a compromise between camera sensitivity settings; set too high would result in more false positives and set too low may not trigger the camera when birds/animals are present. Another issue with camera traps is that it takes time to interpret the photos and videos. Despite these issues there is much to be gained from camera traps by showing the behaviour of hens and how often they are on the outer range. As such, very little resting behaviour was seen on the outer range, with hens actively foraging and walking (Campbell et al. 2020). However, hen behaviour performed while on the outer range maybe season dependent. For instance, dust bathing behaviour was observed by the researcher (no cameras were in place at the time) on the outer range during late spring when soil conditions were dry, with most hens dust bathing under saltbush and blue bush (Maireana brevifolia). Therefore, camera traps are needed at different times of the year to capture seasonal effects on visitation levels to the outer range and the variety of hen behaviour. Distance from the shed had a strong influence on the frequency of visits by hens, with a large reduction in the number of visits at 120 m compared to 70 m. More cameras are required beyond 120 m from the shed to determine whether the number of visits reduce even further.

Even though wedge tailed eagles were among the least frequent visitors to the range their impact was great. One camera recorded a pair of wedgetail eagles simultaneously attacking a hen each, with the two hens trying to reach the cover of saltbush. The other hens nearby initially moved toward the eagles and their attacked flock mates, but soon retreated. Regardless of the eagle attacks, hens returned to the area within 30 minutes and were seen only 3 – 4 metres from the eagles feeding on the hen carcasses. This is contrary to the perception that hens are frightened by birds of prey. Similar behaviour by hens in response to birds of prey was observed in a Dutch study (Bestman & Bikker-Ouwejan 2020). Generally, other wild bird species were not seen often in the same photo or video with hens, and maybe avoiding the hens as suggested by Scott et al. (2018) and Elbers and Gonzales (2020). They were mostly found on the range before pop holes opened and after they had closed, also implying that hens detered wild birds. While hens are on the range there was minimal direct contact with wild birds (except eagle attack), however the biosecurity threat would most likely result from hens contacting wild bird excreta on the range (Scott et al. 2018 and Elbers & Gonzales 2020). Nevertheless, photos and videos would be useful to assess biosecurity risks based on the types of wild birds seen, but field observations of wild birds are also needed (Atzeni et al. 2020). As this study was for only 10 weeks, further camera trapping throughout the year is warranted to cover different climatic seasons, thereby potentially revealing more species of wild birds.

In conclusion, camera traps are a simple and cost-effective way of assessing how often hens go to the outer range areas and what they do while out there. This information would assist with the design of outer range areas to make them more attractive for hens, specifically the need for shelter (e.g. trees and shrubs). Photos and videos from camera traps also provide evidence of the wild bird species that visit the range and the implications for biosecurity.

ACKNOWLEDGEMENTS: Many thanks to Australian Eggs for funding this research and the participation by the farm collaborator.