Breeding ecology of tits Parus spp. using artificial nest boxes in a coniferous forest over a five-year period

Abstract

This study was conducted to clarify the breeding ecology of tits Parus spp. using artificial nest boxes with different entrance diameters in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010. A total of 42 breeding pairs, including varied tit Parus varius, marsh tit P. palustris, coal tit P. ater and great tit P. major utilized the artificial nest boxes during our study period. There were differences in preferred entrance diameter of artificial nest boxes for each species. The 30 mm artificial nest box entrance diameter was used most frequently. For each tit species, there were differences in first egg date, clutch size, brood size, egg incubation period, nestling care period and breeding success over the course of the study. Long-term ecological research is necessary to collect more data on environmental factors to be able to estimate their full consequences in terms of the breeding ecology of Parus spp.

Keywords:

• artificial nest boxes
• breeding ecology
• coniferous forest
• Parus

Introduction

For birds, timing of breeding is crucial because those that produce chicks when food is seasonally most abundant are fittest (van Noordwijk et al. 1995; Cresswell and McCleery 2003). Also, initiation of clutch incubation a few days sooner or later may considerably affect nestling growth and fledging weight, and fledging weight is a determinant of subsequent survival and fitness (Gebhardt-Henrich and van Noordwijk 1991; Naff-Daenzer and Keller 1999).

Recently, seasonal peaks in food abundance have advanced owing to higher spring temperatures (Myneni et al. 1997). Yearly temperature variations may, however, delay or accelerate the food peak after the first egg has been laid (Visser et al. 1998). Climate change may therefore affect the first egg date and peak food abundance differently, depending on the detailed patterning of spring temperatures (Stevenson and Bryant 2000), resulting in either an increase or decrease in the duration of the period between first egg laid and hatched. As such, long-term ecological research is needed to understand avian breeding ecology in relation to climate change.

Artificial nest boxes have been widely used to research the breeding ecology of birds (Matthew et al. 2002; Park et al. 2004) and are normally considered an effective conservation tool for cavity nesting birds. This paper examines the breeding ecology of tits Parus spp. using artificial nest boxes in a coniferous forest. We investigated the breeding schedule from the first egg date to the time of leaving the nest of birds using the artificial nest boxes.

Materials and methods

This study was conducted in a coniferous forest at Ansung Campus, Chung-Ang University (37° 00′ 04″ N, 127° 13′ 96″ E) from March through July, 2006 to 2010. We selected a study site 120 × 240 m in the coniferous forest where pitch pine Pinus rigida was the dominant tree species.

The study site was divided into 30 × 30 m grids marked with flags, facilitating accurate identification of artificial nest box locations (Park et al. 2004). A total of 45 artificial nest boxes were distributed through the study site in January 2005 and positioned 1.5–2 m above the ground in various tree diameters (Rhim and Lee 2005). The artificial nest boxes varied in their entrance diameter from 30 mm, 35 mm and 40 mm to accommodate the different body sizes of cavity-nesting birds.

During March through July of each study year, the use status of the artificial nest boxes was investigated 2–5 days per week. Artificial nest boxes were checked daily around the expected day of hatching to establish the exact hatching date (Sanz and Tinbergen 1999). We surveyed clutch size, brood size, egg incubation period, nestling care period and breeding success of birds using the artificial nest boxes. Breeding success (%) was calculated as the number of nestlings which left the artificial nest boxes/number of eggs laid × 100 (Son 2011).

Results

Tits are very active small birds (Lee et al. 2000) which can be found around villages and in forest areas. During our study, varied tit Parus varius, marsh tit P. palustris, coal tit P. ater and great tit P. major bred in artificial nest boxes over the five-year period.

A total of 42 pairs of tits bred in artificial nest boxes in the coniferous forest area. Artificial nest boxes with 30 mm entrance diameters received the most usage. The mean number of breeding pairs was 8.4 per year. The minimum number of breeding pairs was 6 in 2010 and the maximum was 10 in 2009 ( Table 1).

Table 1. Differences in nest box entrance diameters used by breeding pairs of Parus spp. in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	Entrance diameter (mm)
Year	30 (n = 15)	35 (n = 15)	40 (n = 15)
2006	4	1	3
2007	6	1	2
2008	4	1	4
2009	4	4	2
2010	2	4	-
Total	20	11	11

A total of seven pairs of varied tits bred in artificial nest boxes during the five-year study period. Most of these breeding pairs used the artificial nest boxes with a 40 mm entrance diameter. Two pairs of varied tit bred every year, except 2009 and 2010 ( Table 2).

Table 2. Differences in nest box entrance diameter used by breeding pairs of varied tit Parus varius in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	Entrance diameter (mm)
Year	30 (n = 15)	35 (n = 15)	40 (n = 15)
2006	1	-	1
2007	-	1	1
2008	1	-	1
2009	-	-	1
2010	-	-	-
Total	2	1	4

Most breeding pairs of marsh tits used artificial nest boxes with a 30 mm entrance diameter. The mean number of breeding pairs for this species was 1.6 per year. In 2009, a maximum of three pairs of marsh tit bred in artificial nest boxes, while only one pair bred in 2007, 2008 and 2010. No artificial nest boxes with 40 mm entrance diameters were used by marsh tit during the study period ( Table 3).

Table 3. Differences in nest box entrance diameter used by breeding pairs of marsh tit Parus palustris in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	Entrance diameter (mm)
Year	30 (n = 15)	35 (n = 15)	40 (n = 15)
2006	1	1	-
2007	1	-	-
2008	-	1	-
2009	3	-	-
2010	1	-	-
Total	6	2	-

Coal tits had the highest number of breeding pairs. A total of 15 pairs bred in artificial nest boxes during the five-year study period. Annually, 2–4 pairs of coal tits bred. Most breeding pairs used artificial nest boxes with 30 mm entrance diameters. Only one artificial nest box with a 40 mm entrance diameter was used by coal tit in 2010 ( Table 4).

Table 4. Differences in nest box entrance diameter used by breeding pairs of coal tit Parus ater in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	Entrance diameter (mm)
Year	30 (n = 15)	35 (n = 15)	40 (n = 15)
2006	2	-	-
2007	4	-	-
2008	3	-	-
2009	-	1	1
2010	1	3	-
Total	10	4	1

Most breeding pairs of great tit used artificial nest boxes with 35 mm and 40 mm entrance diameters. The mean number of great tit breeding pairs was 2.4 per year. A total of 12 great tit pairs bred in artificial nest boxes during the study period ( Table 5).

Table 5. Differences in nest box entrance diameter used by breeding pairs of great tit Parus major in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	Entrance diameter (mm)
Year	30 (n = 15)	35 (n = 15)	40 (n = 15)
2006	-	-	2
2007	1	-	1
2008	-	-	3
2009	1	3	-
2010	-	1	-
Total	2	4	6

The first egg dates of varied tit were from 11–18 April. Clutch size was 9.5–10.0 and brood size varied from 4.5–10 each year. The egg incubation period was 18.4–20.1 days and the nestling care period was 14.3–16.3 days. Breeding success differed each year from 47.4–81.8% ( Table 6).

Table 6. Breeding data of varied tit Parus varius using artificial nest boxes in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	2006	2007	2008	2009	2010
First egg date	18 April	16 April	15 April	11 April	-
Clutch size (ea)	9.50 ± 0.71^*	10.00 ± 0.00	9.50 ± 2.12	10.00 ± 0.00	-
Brood size (ea)	4.50 ± 2.12	5.00 ± 0.00	6.00 ± 1.41	10.00 ± 0.00	-
Egg incubation period (days)	20.07 ± 3.78	18.39 ± 2.15	19.27 ± 2.57	18.50 ± 3.03	-
Nestling care period (days)	14.31 ± 0.79	16.27 ± 0.97	15.79 ± 1.02	15.40 ± 0.52	-
Breeding success (%)	47.4	50.0	63.2	81.8	-
^*Mean ± SE.

Marsh tits laid their first eggs from 2–18 April. Clutch size varied from 7.5 to 10.0 and brood size from 3.5 to 8.5 per year. The egg incubation period was 17.4–21.5 days and the nestling care period was 11.4–17.6 days. Maximum breeding success was 50.0% in 2007 and 2010. Minimum breeding success was 37.5% in 2009 ( Table 7).

Table 7. Breeding data of marsh tit Parus palustris using artificial nest boxes in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	2006	2007	2008	2009	2010
First egg date	18 April	13 April	15 April	2 April	18 April
Clutch size (ea)	7.50 ± 2.12^*	10.00 ± 0.00	9.00 ± 0.00	9.00 ± 2.65	10.00 ± 0.00
Brood size (ea)	3.50 ± 0.71	6.00 ± 0.00	5.00 ± 0.00	8.50 ± 0.71	5.00 ± 0.00
Egg incubation period (days)	20.14 ± 3.25	17.38 ± 2.64	19.56 ± 2.37	18.76 ± 3.11	21.50 ± 3.03
Nestling care period (days)	14.31 ± 0.78	13.29 ± 1.04	15.39 ± 0.69	11.38 ± 0.52	17.60 ± 0.55
Breeding success (%)	46.7	50.0	44.4	37.5	50.0
^*Mean ± SE.

The first egg dates of coal tit were from 7–15 April. Clutch size was 7.0–11.0 and brood size varied from 4.3–10.0 during our study period. The egg incubation period was 18.3–20.1 days and the nestling care period was 15.7–16.9 days. Breeding success was different each year, ranging from 46.4–78.9% ( Table 8).

Table 8. Breeding data of coal tit Parus ater using artificial nest boxes in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	2006	2007	2008	2009	2010
First egg date	15 April	9 April	12 April	7 April	10 April
Clutch size (ea)	9.50 ± 0.71^*	9.33 ± 1.53	9.00 ± 2.00	11.00 ± 1.41	7.00 ± 2.94
Brood size (ea)	7.50 ± 3.54	7.75 ± 4.11	6.67 ± 2.52	10.00 ± 0.00	4.33 ± 2.31
Egg incubation period (days)	20.64 ± 3.41	19.54 ± 2.36	18.34 ± 2.67	19.50 ± 3.61	19.18 ± 3.16
Nestling care period (days)	16.97 ± 0.67	15.69 ± 0.95	16.04 ± 0.68	16.30 ± 0.48	16.92 ± 0.95
Breeding success (%)	78.9	69.9	66.7	47.4	46.4
^*Mean ± SE.

Great tits laid their first eggs from 2 April—6 May. In 2010, the first egg date was late compared to other years. Clutch size varied from 5.0 to 10.0 and brood size from 2.5 to 8.0 each year. The egg incubation period was 17.7–19.3 days and the nestling care period was 14.4–15.1 days. Maximum breeding success was 85.7% in 2009 while minimum breeding success was 43.8% in 2007 ( Table 9).

Table 9. Breeding data of great tit Parus major using artificial nest boxes in a coniferous forest at the Ansung Campus, Chung-Ang University from March through July, 2006 to 2010.

	2006	2007	2008	2009	2010
First egg date	17 April	2 April	10 April	6 April	6 May
Clutch size (ea)	5.00 ± 1.65^*	8.00 ± 2.38	7.33 ± 1.15	9.50 ± 0.58	10.00 ± 0.00
Brood size (ea)	2.50 ± 1.12	3.50 ± 1.53	4.67 ± 1.53	8.00 ± 0.82	-
Egg incubation period (days)	17.69 ± 2.57	19.34 ± 3.28	18.97 ± 2.38	18.24 ± 3.00	-
Nestling care period (days)	14.37 ± 1.05	15.12 ± 0.57	14.28 ± 0.97	14.84 ± 1.25	-
Breeding success (%)	50.0	43.8	61.6	85.7	-
^*Mean ± SE.

Discussion

Social dominance of tits is related to body size and mass (Hogstad 1978; Jablonski and Lee 1999). Varied and great tits are highly dominant compared with marsh and coal tits. Also, differences in body size influence the use of artificial nest boxes (Rhim and Lee 2005). Large body-size tits, such as varied and great tits mainly used artificial nest boxes with 40 mm entrance diameters ( Table 2 and 5) while most breeding pairs of marsh and coal tits preferred artificial nest boxes with 30 mm entrance diameters ( Table 3 and 4).

Life-history theory assumes that reproduction is costly and competes for resources with other costly activities performed by individuals (Allander 1997). An individual cannot simultaneously maximize all life-history straits since energy is a limited resource that has to be optimally allocated among different functions (Stearns 1992).

Little is known of how temporal variations affect the breeding ecology of birds. Most studies concerning this relationship have been short-term periods of one or several years (Oddie and Reim 2002). It is possible, if not actually probable, that inter-annual variations in the environment (e.g. population density, nesting place abundance, food resource abundance and operational sex ratio) affect breeding ecology (Yamaguchi et al. 2004). Also, complex changes in temperature patterns may change breeding phenology (Stevenson and Bryant 2000).

Environmental stress may increase time and energy costs during breeding, as a result of nest building, courtship feeding and mate-guarding activities. Also, environmental factors which can influence the abundance of food may differ over years and among populations affecting research outcomes (Allander 1997).

Conclusion

In our study, first egg date, clutch size, brood size, egg incubation period, nesting care period and breeding success differed in the four Parus spp. To effectively clarify breeding ecology of tits, more long-term data on environmental factors are needed to be able to estimate their full consequences in terms of breeding ecology.

Acknowledgements

This study was supported by the Korean National Long-Term Ecological Research (KNLTER) Program of the Ministry of Environment, Republic of Korea.