Determination of development periods of honeybee colony by temperature in hive in Latvia, year 2002
Egils Stalidzans*, Valdis Bilinskis** and Almars Berzonis***
*Institute of Computer Control, Automatics and Computer Technics,
Riga Technical University, 1 Meza Str., Riga, LV 1048, Latvia
**Laeta Ltd “Zvirgzdi”, p/n Rubene, Vaidavas pag.
***Biskopibas Laboratorija SIA, Mazstaldati, Ogres raj., LV 5041, Latvia
All the year 2000 continuous measurement of temperature in honeybee hives is done in Latvia, Riga region. Measurements are recorded after each 15 minutes. Sensors are located above the bee nest, under the pillow. There are six periods existing with different speed of change of average day and night temperature in hive, which possibly correspond to following cycles in bee colony development:
- Brood rearing in cluster with increasing intensity and moving of cluster towards the upper part of nest.
- Intensive brood rearing with dying of wintering bees.
- Brood rearing and food supply.
- Final stage of brood rearing.
- Conversion to wintering period starting in lower part of the nest.
- Wintering in cluster without brood rearing.
Conversions from one period to another are very clearly distinct and possibly characteristic for different climatic zones and subspecies of honeybee.
Generally it can be concluded, that the honey bee colonies start the brood rearing because of some unknown reason and continues with higher correlation to the time than to outside air temperature (1.; 2. and 4. periods). The exception is the 3-rd period, where the biggest influence have the maximal temperatures.
The behaviour of bee colony is close linked to climatic circumstances in the region of living. Phenologists have opinion, that climatic changes are firstly influencing the development of nectar plants, which determines the behaviour in the bee colony1.
In the annual cycle of bee colony two very different periods of behaviour can be observed: passive wintering period and active summer period. It is hard to determine clear border between them. Beekeepers have divided the development of bee colony more detailed: replacement of wintering bees, spring development period, active summer period, preparation for wintering period, period of passive wintering2.
The aim of the paper is to determine the changes of temperature in the hive inhabited by bees during a year under Latvian climatic circumstances to qualify start and end dates of particular periods and their duration.
Materials and methods
Measurements are done in Latvia, Riga district from 1-st January till 31-st December 2000. 14 bee colonies were observed. One of them had Caucasian subspecie (Apis mellifera caucasica) bee queen (V10); one has Buckfast bee queen (4), three colonies have daughters of Buckfast queen, which are naturally inseminated with unfathered drones (V2;V3 and V4). The queens in rest of the observed colonies are unknown mixes (V1, V5-V8, 5-7 and 9). Size of colonies in autumn was from 7 to 11 inhabited frames (435x300 mm each). 10 bee colonies (V1-V10) are living in trailer, where hives are put into two blocks with five 13-frames sections. Thickness of wooden walls is 35±5 mm. Four colonies have cold entrances and one has joint wall; six colonies have warm entrances and two joint walls. The rest of colonies were in single walled (thickness 35±5 mm) 15 frame hives with 120 mm high underframe space. All the colonies are covered by drapery pillows with thickness 8 cm. From 15-th May till 25-th July three colonies swarmed (V5; 7 and 9). In four colonies the queens were changed (V1; V5; V9 and 9). They started egg laying from 1-st of June till 20-th of July. Colonies were fed by sugar syrup from 10-th June till 22-nd June.
As temperature sensors are used DS 1820 (Dallas Semiconductor) type of sensor. Measurements were controlled and registered by computer. In each hive above the nest under the pillow (further – temperature in hive) in the place of maximal temperature (determined experimentally) was placed a sensor. Location of the sensor was changed seldom: observing or extending nest. Outside temperature is measured by two sensors very near from the hives, at their northern side in the shadow on the height of pillows. The sensors are connected between themselves and the computer by cables. Measurements were done all the day and night each 15 minutes during all the time of experiment.
From the measurements of one day and night the average hive and average, maximal and minimal ambient air temperatures were calculated. Average day and night hive and outside air temperature changes during the year are described by polynomial equation of 4-th order, but the temperature changes in hives with linear equations as well dividing the year cycle in 6 characteristic periods.
Changes of average day and night temperatures in honeybee inhabited hives and ambient air are displayed in the Figure 1. Change of average temperature in hives (th) and ambient air (ta) are described by equations:
th = 2,897.10-8.x4 - 1,966.10-5.x3 + 3,384.10-3.x2 - 0,022.x + 12,7;
ta= 2,104.10-8.x4 - 1,616.10-5.x3 + 3,441.10-3.x2 - 0,122.x + 0,7;
Coefficient of correlation between the mentioned values is r = 0,85.
Changes of beehive temperatures during a year are split into 6 characteristic periods (Figure 2) and each of them is described by a linear equation:
ti = ai . x + bi;i = 1 - 6;
where x – day counting from the 1-st January; ai and bi coefficients of linear equations in the period i.
Figure 1. Changes of average temperature of hive temperatures th (t1 and t2, minimal and maximal temperatures respectively) and of average temperature of ambient air (ta) in Latvia, year 2000. Black lines are approximations of th and ta
Figure 2. Periods of changes of average honeybee hive temperatures (1-6) and ambient air temperature (ta) in Latvia, 2000
Table 1.Coefficients (ai and bi) of the linear equations of changes of average hive<br>temperatures th in particular periods. Coefficient ai characterises the speed of temperature changes<br>in the hive during the respective period °C/d.
Table 2. Statistical values of the average day and night temperatures in hives th in particular
Table 3. Statistical values of the average day and night temperatures of ambient air ta in particular
Dates of conversions from one period to another in 2000 under Latvian circumstances in described case are described in table 4.
Table 4. Dates, when the temperature cycles of bee colonies converse from one to the next
Table 5. Values of correlation coefficients r between hive temperature and time, minimal,
average and maximal temperatures in particular periods.
Behaviour of bee colonies in the 1-st, 2-nd and 4-th periods has the best correlation with time, in the 3-rd and 5-th with maximal air temperature and in the 6-th with the average air temperature.
The chosen frequency of measurements 15 min assured sufficient accuracy of investigations for measurements of outside air (P~3%) and excellent in hives (P~0,3%). Estimating the findings it can be assumed, that particular periods correspond to following behaviour of the bee colony:
- Brood rearing with increasing intensity in cluster and moving of cluster upper part of the
- Intensive brood rearing with replacement of the wintering bees generation;
- Brood rearing and food collection;
- Final stage of brood rearing;
- Conversion period to the wintering stage. Bees move to lower part of the nest
- Broodless wintering in cluster
During the first period, which takes 81 days, supposably, brood rearing in cluster with cluster movement to the upper part of the nest takes place. Temperature in the hive has the best correlation with time (r = 0.96), but the influence of the average ambient temperature is the lowest during all the year (r = 0.34). A bit bigger influence has the maximal temperature of the day (r = 0,49). The difference between colonies is characterised by variation coefficient v = 7.9 %, which can be estimated as an average one. Increase of temperature in this period indirectly confirms fact, that brood rearing in the cluster takes place with growing intensity3.
In the second period, which is 28 days long, the beginning of intensive brood rearing and course of further temperature changes determines time (r = 0.92) and ambient air temperature (r = 0,76). Diversity among the hives grows (v = 12,6%) because of differences in behaviour in time. The obtained results state, that the used methodology of temperature measurement can be used to study behaviour of different bee subspecies in different regions during the start of intensive brood rearing in different geographical regions. That would allow estimate their fitness for given climatic circumstances.
In the third period, which is the longest - 127 days, the average temperature above the nest under the pillow reaches 32,4 °C, which is just 3 °C lower, than the temperature in the brood rearing zone, but the diversity is the lowest during all the year (v = 0,8%). The highest influence have maximal temperatures of the day (r = 0,70)
During the fourth period (30 days long) the diversity of temperatures is the biggest (v = 20,9%), which denotes on higher heterogeneity in behaviour of bee colonies in time, when the rearing of wintering bees continues. Bee behaviour correlates with time (r = 0,96), as well as the average and minimal day and night temperatures (r = 0,89 and r = 0,88 respectively). In the fifth period, which takes 49 days the diversity of temperatures decreased (v = 7,7%), what may be connected with end of brood rearing. Highest impact have maximal day temperatures (r = 0,9).
In the 51 day long sixth period temperature in the hive above the cluster under the pillow decrease till 11,8 °C and variation coefficient till = 2,8%, in spite of the highest diversity of temperatures outdoors (v = 15,6%). Influence of outside temperature decrease (r = 0,65), but the behaviour of bees practically does not change in time (r = 0,04).
Altogether it can be concluded, that the colonies of honeybee start brood rearing because of influence of circumstances, which are unknown at the moment. Brood rearing is continued correlating the best way with time and leaving secondary part for the ambient temperature. That is stated by higher correlation coefficients against time, than against ambient air temperatures (periods 1; 2 and 4). Exception is the third period, where the biggest influence have maximal day temperatures.
During the fifth period, when, supposably, there is a little amount of brood or no brood, the mean influence have maximal day temperatures and time, but in the sixth – average temperatures.
- There are six characteristic periods observed measuring temperature changes above the nest of the colony under the pillow in 2000 in Latvia, which differ by speed of temperature change: period from 1.01.00 till 21.03.00 (0,118 °C/d); from 21.03.00 till 18.04.00 (0,418 °C/d); from 18.04.00 till 23.08.00 (-0,012 °C/d); from 23.08.00 till 22.09.00 (-0,414 °C/d); from 22.09.00 till 11.11.00 (-0,138 °C/d) and from 11.11.00 till 31.12.00 (-0,005 °C/d).
- For bee behaviour during winter, supposably, rearing brood in cluster (1. period) and in spring – during intensive brood rearing (2. period), as well as in the final stage of brood rearing (4. period), ambient temperature has secondary significance. Higher correlation with hive temperature has time.
- Biggest influence of maximal day and night air temperature on the temperature in hives over the nest (cluster) is in late spring-summer period, when brood rearing and food collection takes place (3. period) and in autumn during the forming of cluster (5. period).
- Influence of outside air temperature on the temperature in hives is the lowest in the first part of winter, when bees are broodless in cluster (6. periods).
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- Szabo T.I. 1993. Brood Rearing in Outdoor Wintered Honey Bee Colonies. ABJ, v. 133, No 8, 579-580