Long-term nest-box study of breeding Tree Swallows

Transcription

1 Long-term nest-box study of breeding Tree Swallows Available for a new Principal Investigator Slides describe project, database, strengths of study - and some of results to date

2 Study period to date: Principal Investigator: David J. T. Hussell Ontario Ministry of Natural Resources Operated as a project of Long Point Bird Observatory, Bird Studies Canada

3 A LONG-TERM STUDY OF TREE SWALLOWS Description of sites Objectives Fieldwork The data Strengths & the future Selected results

4 The 3 study sites are located at Long Point on the north shore of Lake Erie

5 Tree Swallows have been studied at PT since 1969 and intensively at PT, SL, and either BF or MC since 1977.

6 BF = Backus Field MC = Mud Creek PT = Tip of Long Point SL = Sewage Lagoons

7 SITES Each site currently has about 60 nest boxes. Boxes are in lines or grids, with nearest neighbour normally 24 m distant Occupancy is high normally %. A few boxes occupied by Eastern Bluebirds (at Mud Creek only), House Wrens, or House Sparrows. Nest boxes are protected from terrestrial predators by predator guards and grease on the poles.

8 Temperature and laying date differ among the sites Mean maximum daily temperature ( o C) Range of annual median dates of first egg PT SL 10 May 1-5 May 6-10 May May May May May 31 - Jun 4 Jun 5-9 Jun Jun Jun Jun Jun 30 - Jul 4 Jul 5-9 Jul day mean maximum temperatures at PT and SL, 1 May - 14 July,

9 Insect abundance also differs among sites. Insect abundance and egg-laying, averaged over 8 years:

10 OBJECTIVES TO DATE (1) maintain a long-term record of breeding performance in relation to insect abundance and weather, (2) conduct other short-term research, consistent with maintaining the long-term record, (3) train students and volunteers in field ornithology.

11 FIELDWORK Conducted mainly by volunteers, funded by Long Point Bird Observatory/Bird Studies Canada Intermittent short-term help from graduate students and other university-based researchers No grants to support long-term fieldwork

12 More than 100 students and other volunteers took part in fieldwork,

13 Blue = ASY Blue = ASY Brown = SY NEST DATA

14 NEST DATA Routine nest data include: Daily checks of nest contents during egg-laying Marks and weights of eggs Twice or thrice daily checks of nest contents during hatching period and weights of nestlings when first seen. Weights and length of primary 9 at brood mean age 12 days Length of primary 9 at 16 days Band numbers of nestlings Band numbers of adults plus age of female (SY or ASY) Additional data include codes for predation or other disruptions and for experiments -- to allow appropriate selection of data for particular purposes.

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16 NEST DATA ARE ENTERED IN EXCEL FILES Female Male Clutch NB No. no. no. bag bag egg age D Site Year Age F Band No. M Band No. No. SZ seq Box mdy time eggs new mk &egg wt. min max P Comments S S S S S S S S S S S S S S S S S S S S S S S S S S S

17 NEST DATA 3 Excel files for each site in each year - laying and egg stage - hatching to fledging - growth of young Files include cross-references to facilitate merging Total of 284 Excel files ( )

18 WEATHER Rain Gauge and Maximum-Minimum Thermometer in a shelter at each site

19 WEATHER DATA Morning and evening readings at each site: Maximum, minimum and current temperatures Rainfall since last observation Cloud cover Wind speed and direction

20 Weather data are entered in Excel files SL temp temp temp temp temp wind wind wind remarks site year month day time min L R max C/F raincloud dir speed units C 4 SW 8 MPH THERM 2 INSTAL C 0 1 SW 6 MPH C 0 3 WSW 3 MPH C 6 7 NW 11 MPH C 0 5 NNE 4 MPH C 0 2 ESE 5.5 MPH C 0 4 NE 5 MPH C NW 3 MPH C 8 10 NNE MPH C N MPH RAINING C 4 10 N 1 MPH C 1 10 W 2 MPH DRIZZLE C NNW MPH LIGHT RAIN C 0 1 SSW 7 MPH C T 10 SSW 9 MPH RAIN C 0 10 WNW <1 MPH C 6 10 SW MPH LIGHT RAIN C 0 8 W 6 MPH C 0 4 W 5 MPH C 0 4 W 5 MPH C 0 4 SW 6 MPH C 0 8 N MPH NO WIND C 0 9 S 3 MPH

21 Weather SINCE 2006, Davis Pro Weather Station at BSC HQ (Port Rowan) records every 30 minutes Temperature Rainfall Relative humidity Wind speed and direction Solar radiation

22 INSECTS INSECTS Abundance of flying insects assessed with 2 or 3 drift nets at each site. Insects drift passively into nets which rotate into the wind.

23 INSECTS Daily samples at each site Mainly May and June, Counted by order or suborder and body length (1-3 mm to mm) Entered in Excel files (76 columns) Dry biomass calculated Adjusted for wind speed at the nets Insect Biomass Index (IBI) Insect Number Index (INI)

24 INSECTS & WEATHER Insect Biomass Index (IBI) Insect Number Index (INI) IBI and INI for each day and site averaged for 2 or 3 nets at each site. IBI and INI also available for each insect size and taxonomic category, for each day and site. IBIs, INIs, and weather data for each day and site merged in SAS files.

25 LONG-TERM STUDY OF TREE SWALLOWS 32 years in present format: Have we learned everything we can learn? Continue or Stop?

26 THE FUTURE? Potential benefits of continuing: 1. Excellent knowledge of the system benefits short-term studies 2. Insights from unusual events 3. Collaboration in new wide scale research programs (e.g. Golondrinas 4. More data will allow refinement of weather and food effects on breeding performance 5. Documentation of climate change effects

27 LONG-TERM STUDY OF TREE SWALLOWS STRENGTHS of this data set/project: 3 sites that differ in insect abundance, spring temperatures and timing of laying. Assumption: all swallows and nests at each site are exposed to the same environmental variables. Therefore: 3 data points per year that we can relate to environmental variables about 90 data points so far, enabling us to consider at least 9 variables simultaneously (or up to 18 if we want to push assumptions to the limit).

28 LONG-TERM STUDY OF TREE SWALLOWS STRENGTHS of this data set/project: Site characteristics and normal effects of weather and insect abundance are well understood, allowing identification of unusual conditions A high percentage of breeders are returnees -- known age or known minimum age: 60-70% -- known exact age: ~ 33%

29 LONG-TERM STUDY OF TREE SWALLOWS STRENGTHS of this project: Tree Swallows are abundant No nest searching High occupancy Minimal predation High fledging success Tolerant of disturbance and experimental manipulations

30 LONG-TERM STUDY OF TREE SWALLOWS STRENGTHS of this project: Volunteer help, accommodation and some lab space available via LPBO/BSC Swallowmobile available for transportation Low cost

31 SELECTED RESULTS 1) Clutch size and insect abundance 2) Coping with a variable environment 3) Spring temperatures, timing of laying, and climate change predictions 4) Influence of spring temperatures and insect abundance on timing of laying and clutch size

32 1) CLUTCH SIZE AND INSECT ABUNDANCE FROM: Hussell, D.J.T., and T.E. Quinney Food abundance and clutch size of Tree Swallows Tachycineta bicolor. Ibis 129:

33 1) CLUTCH SIZE AND INSECT ABUNDANCE Annual mean clutch sizes versus insect abundance at 3 sites over 8 years, CONCLUSION: Clutch size depends on insect abundance, both among sites and among years within sites. Tree Swallows appear to adjust their clutch sizes to the local conditions at the time of laying.

34 1) Clutch Size versus Laying Period Insect Abundance

35 2) COPING WITH A VARIABLE ENVIRONMENT Swallow tactics for dealing with a variable environment delay start of egg-laying vary clutch size terminate clutch early skip laying extend incubation young store fat in good times young reduce growth in bad times young delay fledge in bad times

36 A UNIQUE EVENT: LONG POINT 1979 Never repeated in 29 years.

37 2) COPING WITH A VARIABLE ENVIRONMENT Swallow tactics for dealing with a variable environment delay start of egg-laying vary clutch size terminate clutch early skip laying extend incubation young store fat in good times young reduce growth in bad times young delay fledge in bad times

38 LONG POINT 1979

39 3) SPRING TEMPERATURES AND LAYING DATES Range (among years) of temperature and date of clutch initiation: Site(s) Range of mean maximum daily temperatures (1-20 May, º C) Range (days) in median date of clutch initiation N Long Point Sewage Lagoon Backus Field Mud Creek ALL COMBINED

40 Influence of maximum daily temperatures and site on median dates of clutch initiation From: Hussell, D.J.T Climate change, spring temperatures and timing of breeding of Tree Swallows (Tachycineta bicolor) in southern Ontario. Auk 120: Variable Regression Coefficient Intercept Standardized Coefficient P T1 (1-5 May) < T2 (6-10 May) < T3 (11-15 May) T4 (16-20 May) SL < SL=1 when site is Sewage Lagoon; otherwise SL=0. n = 80. R 2 =

41 IMPLICATIONS FOR CLIMATE CHANGE Observed range of mean maximum daily temperature, 1-20 May, all years, all sites = 10.6ºC What will happen if global climate change results in an increase of 5ºC? The regression predicts an average advance of laying date = 7.3 days Observed range of median laying date = 19 days THEREFORE: TRES can easily adjust timing

42 4) Relationships between temperature, food abundance, laydate and clutch size in Tree Swallows, Tachycineta bicolor. David Hussell and Judith Phillips

43 PATH ANALYSIS: HYPOTHESIS Site Pre-laying period food abundance Temperature Median date of first egg Laying period food abundance Mean clutch size Site

44 Site Pre-laying period food abundance Temperature TEST: FULL MODEL Laying period food abundance Median date of first egg Mean clutch size Site Site Site

45 RESULTS: for 2 sites only, SL and LP Temperature Median date of first egg Site Pre-laying period food abundance Site Site Laying period food abundance Mean clutch size Site N=45

46 Acknowledgements Long Point Bird Observatory, Bird Studies Canada Norfolk County Long Point Region Conservation Authority Ontario Ministry of Natural Resources Canadian Wildlife Service Canadian Department of Transport Mr. and Mrs. R.C. Stanley Climate Change Action Fund, Natural Resources Canada Climate Change Program, Ontario Ministry of Natural Resources Michael Bradstreet, Erica Dunn, Diane De Steven, Charles Francis, Judith Phillips, Terry Quinney, Stephen Yezerinac Staff of Long Point Bird Observatory More than 100 field assistants and volunteers

47 Interested in taking over? Continuation of traditional data-collection protocols is not a condition Contact David Hussell David.Hussell@ontario.ca