In an effort to determine the effects of the orientation of hive entrance on honey bee colony activity and temperature, hives were placed facing different cardinal directions (3-5 hives per direction). Hive weight was recorded every 5 minutes and temperature every 30 minutes from April 2019 to June 2020. Daily weight data were analyzed using piecewise regression. In southern Arizona from December to March, hives facing east started daily flight activity 50 minutes earlier than hives facing west, and ended flight activity 57 minutes earlier than hives facing south. During that period east-facing hives also lost only 62 g per d while north-facing hives lost about 100 g per d. East-facing hives were also about 7°C cooler on average than west-facing hives, although that may have been due to the movement of bee clusters within the hive. From December to March hives facing east also had significantly lower morning weight loss due to departing foragers than hives facing north (indicating more foragers) but higher weight loss from April-June 2020. Most effects were observed from December to March, probably due to restricted daylight hours and lower ambient temperatures. No significant effects were observed with respect to visually-estimated adult bee numbers (frames of bees) or the surface areas of sealed brood. We recommend hive orientation be taken into account in the design of field experiments that involve monitoring colony activity.

On 1 April 2019, 20 mature bee colonies (at least one year old) were identified in an apiary north of Tucson, Arizona, USA (Latitude: 32.55°; Longitude: -111.35°). All hives were queen right with no visible signs of disease. Each hive contained a minimum of 1 kg honey bees in 1-2 painted, 10-frame, wooden Langstroth boxes (43.7 l capacity) (Mann Lake Ltd., Hackensack, MN) with migratory wooden lids. Hives were placed on stainless steel electronic scales (Tekfa model B-2418 and Avery Weigh-Tronix model BSAO1824-200) (max. capacity: 100 kg, precision: ±20g) and linked to 16-bit dataloggers (Hobo UX120-006M External Channel datalogger, Onset Computer Corporation, Bourne, MA) with weight recorded every 5 minutes. A temperature sensor (iButton Thermochron, precision ±0.06°C) enclosed in plastic tissue embedding cassettes (Thermo Fisher Scientific, Waltham, MA) was stapled under the center of the top bar on the 5th frame in the bottom box of each hive and set to record every 30 min. Hives were arranged in a square pattern around a central box that contained the batteries and electronic gear. Hives within such a group were 0.5- 1 m apart and groups were >3 m apart.

Prior to the start of the experiment, the frames of bees (FOB) was visually estimated (Delaplane et al. 2013). Hives were randomly assigned a treatment group, with hives in a given group having the entrance facing the same cardinal direction (east, north, south or west). Because the size of the honey bee colony may be expected to impact data on hive weight and temperature, and because a clumped distribution of bee colony sizes may occur even in randomly-assigned treatment groups (Hurlbert 1984) care was taken to avoid a clumped distribution by selecting a design with the least clumping. To adjust the hive entrance orientation to a new orientation, hives were slowly moved and rotated into position over a period of 2-10 d, depending on how much the hive had to be moved. Care was taken to avoid moving hives in a way that would confuse returning foragers. Hives were inspected on 21 June, 18 July, 14 August, 12 September and 10 October, 2019, and on 27 February and 19 June, 2020. During each inspection, FOB was visually estimated, all frames containing sealed brood were photographed, and hive queen status was determined. Missing or supersedure queens were replaced. All queens except two were replaced at least once between April and December 2019. The area of sealed brood per frame was estimated from the photographs using ImageJ version 1.47 software (W. Rasband, National Institutes of Health, USA) or CombCount (Colin et al. 2018). During the course of the experiment the number of hives in each treatment group changed as hives died and were replaced, but each group had at least three hives throughout the experiment.

Missing values are entered as -999. 

Hive weights are in kg.

Hive temperatures are in degrees Celsius.

Brood surface area is in square centimeters.