Extra-pair Fertilizations: A Cost-reducing Mating Strategy in Hybridizing Chickadees?

1. Extra-pair Fertilizations: A Cost-reducing Mating Strategy in Hybridizing Chickadees? Matthew W. Reudink

2. Avian Mating Systems • Polygyny, Polyandry, Polygynandry…. • Social Monogamy • Common in species with altricial young • Common in Passerines

3. Mating Systems in Birds • Social monogamy • Male and female with a pairbond • Usually both care for young at the nest • Genetic monogamy • Social parents sire all offspring • Social monogamy ≠ genetic monogamy?

4. Extra-pair Fertilization • Fertilization of offspring by an individual other than the social partner • Common: 90% of bird species studied • Average: 30% of nests, 10-15% of offspring

5. Extra-pair Paternity • Males: more offspring the better • Females actively pursue extra-pair copulations (EPCs) • Good Genes • Which females cheat? • Females socially paired with low quality males • Who are the extra-pair sires? • High quality males

6. Good Genes and Hybrid Zones • Reproductive costs of hybridization • Mixed pairing: “poor genes” • Conspecific pairing: “good genes”

7. Good Genes and Hybrid Zones • Female pursuit of EPCs as a cost-reducing mechanism (Veen et al. 2001) • Pied and Collared Flycatchers • High rates of EPCs • Females in mixed pairs had EPCs with conspecifics www.birdguides.com

8. Mixed Pair with Hybrid Young Black-capped Male Carolina Female HY HY HY HY HY HY

9. Extra-pair Copulation Black-capped Male Carolina Female EPC Carolina Male Pure HY HY HY Pure HY Pure HY HY

10. Microsatellite DNA • Simple sequence repeats of 2-6 bases • Amplified via PCR • Highly variable segments of DNA • Used for both creating hybrid indices and parentage analysis Forward Primer Microsatellite Reverse Primer AT AT AT AT AT * Fluorescent Tag Flanking Regions

11. Goals of Project • Examine the distinctness of “pure” Black-capped and Carolina populations • Investigate genetic structure of the Nolde Forest hybrid population • Examine extra-pair paternity and mate choice in a chickadee hybrid zone • Which females are pursuing EPCs? • Who are females choosing as EP partners? • Are nests with EPO “better off”?

12. Why Chickadees? • Black-capped Chickadees engage in EPCs • Otter et al. (1998), Mennill et al. (2004) • Carolina Chickadees engage in EPCs • R. Curry & A. Ruscica, unpubl. • Black-capped and Carolina Chickadees hybridize across their range overlap • Ohio, Bronson et al. (2003); Missouri, Sawaya (1990); Appalachians, Sattler and Braun (2000); Pennsylvania: Mullen (2000), Cornell (2001), Rossano (2002)

13. Black-capped / Carolina Chickadee Ranges

14. Chickadees Black-capped Carolina Hybrid

15. Field Methods • Hawk Mountain: Black-capped • Nolde Forest: Hybrid Zone • Great Marsh: Carolina

16. 665ha area Mixed forest habitat 2000-2003 152 nest tubes, 14 nest boxes N = 90 nests N = 477 offspring Nolde Forest Study Site Reading, Berks Co., PA

17. Capture and Banding • Capture • Adults: net or trap, at nest or feeder • Nestlings: from nest • Banding • FWS numbered metal band • 2-3 color bands

18. Blood Sampling • Blood sampled at time of banding • 30-50 μl from ulnar vein • Samples stored in lysis buffer

19. DNA Extraction PCR amplification of 6 microsatellite loci mtDNA Haplotypes Paternity Exclusion Iterative Assignment Test Baseline Hybrid Index Paternity Assignment Contact Zone Hybrid Index Mate Choice Analysis Molecular Methods

20. N = 4 4 31 10 mtDNA Haplotypes Hawk Mountain (Black-capped) 12 32 22 19 41 29 Carolina Haplotype % Haploytpes Black-capped Haplotype Nolde Forest (Hybrid) 14 16 1 20 21 13 Great Marsh (Carolina)

21. Hybrid Index Scores N = 75 N = 24 N = 45 Carolina-like Black-capped-like

22. Now on to paternity analysis…

23. Questions About EPFs 1) Are EPFs occurring? 2) Are EPF rates high relative to parental populations? 3) Which males are being “cheated on”? 4) Who are females choosing as extra-pair partners? 5) Are nests with EPO “better off” than those without EPO?

24. Extra-pair Paternity? YES N = 10 21 31 28 Total: EPO in 56% of nests 49 108 164 156 Total: 26% of offspring = EPO

25. Social Pairs and Paternity • Does probability of EPO increase with genetic dissimilarity of social pair? • NO(Wald 2=2.3, df=1, P=0.13) • Do females choose extra-pair males more like themselves? • NO (F1,36 = 0.0295, P = 0.86) • Chickadees ain’t flycatchers!

26. Females paired with Black-capped-like males N = 50 nests Some EPO Logistic Regression N = 40 nests All WPO Male Hybrid Index Black-capped-like Carolina-like Wald 12 = 8.82, P = 0.003 Which Females Cheat?

27. Extra-pair sires are more Carolina-like than social males Social Male Extra-pair Sire Who are the extra-pair sires? Carolina-like Males t58 = -2.616, P = 0.01

28. When males did not interact, females chose conspecifics Mate Choice Aviary Experiment Carolina Black-capped Black-capped Bronson et al. 2003

29. Removed visible barrier and allowed males to interact through screen Mate Choice Aviary Experiment Carolina Black-capped Black-capped Bronson et al. 2003

30. Mate Choice Aviary Experiment • Carolina males were dominant over Black-capped males Carolina Black-capped Black-capped Bronson et al. 2003

31. Mate Choice Aviary Experiment • Females always chose dominant males • Mate choice may be playing a role in the northward movement of the chickadee hybrid zone Black-capped Carolina Black-capped Bronson et al. 2003

32. Take Home Messages • Chickadees hybridize…..A LOT! • Chickadees cheat….A LOT! • It’s good to be a Carolina Chickadee!

33. Tracking the year-round ecology and behaviour of migratory birds Dr. Matt Reudink Assistant Professor, Dept. of Biological Science, TRU

34. Tracking behaviour and ecology throughout the annual cycle 1 Queen’s University & Smithsonian Institution

35. What determines winter habitat quality? Reudink et al. 2009. J. Avian Biol.

36. Mangrove Scrub Sex/age bias Maintain/gain mass Winter habitat quality low stress levels early departure Marra & Holmes (2001) Auk; Studds et al. (2005) Ecology

37. Mangrove Scrub Mangrove Scrub 12 first-year 24 adult 12 first-year 14 adult

38. hue, saturation, brightness measures flanks tail reflectance (%) wavelength (nm)

39. Plumage differs between habitats two-way ANOVA habitat: F = 7.82, p = 0.007 age: F = 3.71, p = 0.06 habitat x age: F = 1.05, p = 0.31 scrub

40. 13C 12C isotopes N N N + N P P N N P P N N N N P P P P N P N P P P N N Ratio of 13C/12C relative to std = d13C, expressed in ‰

41. CO2 -22‰ -24‰ -26‰ -30‰

42. CO2 -21‰ -19‰ -17‰ -13‰

43. Mangrove Scrub C3 plant dominated low water stress highly negative d13C C4 plant dominated high water stress more positive d13C

44. Mangrove Scrub C3 plant dominated low water stress highly negative d13C C4 plant dominated high water stress more positive d13C Claw signatures

45. Stable-carbon isotope analysis • Captured males within 7 days • Sampled 2mm segment of claw • Analyzed for 13C claw

46. The pattern holds… n = 15 adult males r = 0.31, p = 0.03

47. Does winter territory quality carry-over to the breeding season? Reudink et al. 2009. Proc. Roy. Soc. B

48. Carry-over effects of winter habitat quality early arrival winter habitat quality (13C) condition Marra et al. 1998. Science

49. Carry-over effects of winter habitat quality Carry-over effects of winter habitat quality apparent success early arrival winter habitat quality (13C) Norris et al. 2004. Proc. Roy. Soc. B

50. Carry-over effects of winter habitat quality paternity early arrival total success winter habitat quality (13C) polygyny Reudink et al. 2009. Proc. Roy. Soc. B