Threats to Biodiversity: A Case Study of Hawaiian Birds

In-Class Exercise

  1. Examine the data presented in Table 1. How many of these species are currently extinct? What other trends do you notice? What factors might contribute to these trends?
Table 1. Status of native birds breeding in the Hawaiian Islands.
GroupSpecies Known to Have ExistedCurrent SpeciesEndangered or Threatened SpeciesNumber of Extinct Species
Seabirds22+222
Herons110
Ibises20-
Waterfowl1133
Hawks311
Rails1122
Stilts111
Owls410
Crows311
Honeyeaters622
Old World Flycatchers110
Old World Warblers111
Hawaiian Thrushes632
Honeycreepers45209
Totals117+5924
Table 1 modified from Scott, J.M., C.B. Kepler, C. van Riper III, and S.I. Fefer. (1988). Conservation of Hawaii's vanishing avifauna. Bioscience 38(4):238–253.





  1. One factor that leads to a decline in biodiversity is the introduction of non-native species. However, most species that are introduced to an area do not become established. What are some characteristics of species that might make them more likely to thrive in a new habitat?



  2. Several species of large rats arrived to Hawaii as stowaways on ships. These rats live in a variety of habitats and eat a variety of foods, both plants and animals. Speculate about how these introduced rats could directly and indirectly affect native bird species.



  3. Researchers hypothesize that several factors may affect the extent of predation by rats on birds. These factors include bird size, nesting site, and the amount of time young spend in the nest (duration of egg incubation and nestling period). Formulate one hypothesis and its accompanying null hypothesis about how one of these factors might affect predation.
    1. Bird size:
      • H1 (hypothesis):
      • H0 (null hypothesis):
    2. Nesting site:
      • H1 (hypothesis):
      • H0 (null hypothesis):
    3. Incubation and nestling period:
      • H1 (hypothesis):
      • H0 (null hypothesis):
  4. Examine the data given to you (Table 2a, 2b, or 2c). Does the data support or refute your hypothesis?
Table 2a. Predation by rats (R. rattus and R. exulans) on birds. Included in this table are the typical stages of life at which rats prey upon the species of bird listed, the population trends of each bird species since rats were introduced, and the size of each bird measured as the average length of male and female birds.
Bird SpeciesStage of Life-Cycle Preyed UponEffect on PopulationSize (cm)
Diomedea immutabilis
(Laysan Albatross)		ChicksContinuing coexistence with rats81
Diomedea nigripes
(Black-footed Albatross)		ChicksMinor81
Pterodroma hypoleuca
(Bonin Petrel)		Eggs, chicksMajor decline30
Pterodroma phaeopygia sandwichensis
(Hawaiia Dark-rumped Petrel)		ChicksNearly 40% of eggs and chicks destroyed during 2-year study43
Phaethon rubricauda
(Red-tailed Tropicbird)		Eggs, chicksUp to 65% and 100% losses of eggs and chicks respectively in some years102
Puffinus pacificus
(Wedge-tail Shearwater)		Eggs, ?chicksMinor43
Fregata minor
(Great Frigatebird)		AdultsMinor94
Porzana palmeri
(Laysan Rail)		UnknownExtinction15
Sterna fuscata
(Sooty Tern)		Eggs, chicksContinuing coexistence with rats43
Sterna lunata
(Grey-backed Tern)		Eggs, chicksAll young destroyed in one year38
Telespyza cantans
(Laysan Finchbill)		UnknownExtinction19
Table 2a modified from:
° Atkinson, I. A. E. 1985. The spread of commensal species of Rattus to oceanic islands and their effects on island avifaunas. In P. J. Moors (ed.), Conservation of Island Birds. pp. 35–81. ICBP Technical Publication No. 3.
° Pratt, D. H., Bruner, P. L., and Berrett, D. G. 1987. A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton, NJ: Princeton University Press.


Table 2b. Predation by rats (R. rattus and R. exulans) on birds. Included in this table are the typical stages of life at which rats prey upon the species of bird listed, the population trends of each bird species since rats were introduced, and the usual nest location for each species.
Bird SpeciesStage of Life-Cycle Preyed UponEffect on PopulationUsual Nest Situation
Diomedea immutabilis
(Laysan Albatross)		ChicksContinuing coexistence with ratsGround surface
Diomedea nigripes
(Black-footed Albatross)		ChicksMinorGround surface
Pterodroma hypoleuca
(Bonin Petrel)		Eggs, chicksMajor declineBurrows
Pterodroma phaeopygia sandwichensis
(Hawaiia Dark-rumped Petrel)		ChicksNearly 40% of eggs and chicks destroyed during 2-year studyBurrows
Phaethon rubricauda
(Red-tailed Tropicbird)		Eggs, chicksUp to 65% and 100% losses of eggs and chicks respectively in some yearsGround surface
Puffinus pacificus
(Wedge-tail Shearwater)		Eggs, ?chicksMinorBurrows
Fregata minor
(Great Frigatebird)		AdultsMinorBranches < 3m high
Porzana palmeri
(Laysan Rail)		UnknownExtinctionGround surface
Sterna fuscata
(Sooty Tern)		Eggs, chicksContinuing coexistence with ratsGround surface
Sterna lunata
(Grey-backed Tern)		Eggs, chicksAll young destroyed in one yearGround surface
Telespyza cantans
(Laysan Finchbill)		UnknownExtinctionOn or near ground
Table 2b modified from Atkinson, I. A. E. 1985. The spread of commensal species of Rattus to oceanic islands and their effects on island avifaunas. In P. J. Moors (ed.), Conservation of Island Birds. pp. 35–81. ICBP Technical Publication No. 3.


Table 2c. Predation by rats (R. rattus and R. exulans) on birds. Included in this table are the typical stages of life at which rats prey upon the species of bird listed, the population trends of each bird species since rats were introduced, incubation and nestling periods for bird species. The incubation period is determined as the number of days from egg laying to hatching. Nestling period is determined as the number of days from hatching to fledging.
Bird SpeciesStage of Life-Cycle Preyed UponEffect on PopulationIncubation Period (Days)Nestling Period (Days)
Diomedea immutabilis1,4
(Laysan Albatross)		ChicksContinuing coexistence with rats62–67140
Diomedea nigripes1,4
(Black-footed Albatross)		ChicksMinor62–67165
Pterodroma hypoleuca2,3
(Bonin Petrel)		Eggs, chicksMajor decline48.7Unknown
Pterodroma phaeopygia sandwichensis1
(Hawaiia Dark-rumped Petrel)		ChicksNearly 40% of eggs and chicks destroyed during 2-year study50–55115
Phaethon rubricauda3,4
(Red-tailed Tropicbird)		Eggs, chicksUp to 65% and 100% losses of eggs and chicks respectively in some years40–50Unknown
Puffinus pacificus1,4
(Wedge-tail Shearwater)		Eggs, ?chicksMinor48–6360–90
Fregata minor1,4
(Great Frigatebird)		AdultsMinor51–57166
Porzana palmeri
(Laysan Rail)		UnknownExtinctionUnknownUnknown
Sterna fuscata3,4
(Sooty Tern)		Eggs, chicksContinuing coexistence with rats27–3316
Sterna lunata4
(Grey-backed Tern)		Eggs, chicksAll young destroyed in one year24–35Unknown
Telespyza cantans
(Laysan Finchbill)		UnknownExtinctionUnknownUnknown
Table 2c modified from Atkinson, I.A.E. 1985. The spread of commensal species of Rattus to oceanic islands and their effects on island avifaunas. In P. J. Moors (ed.), Conservation of Island Birds. pp. 35–81. ICBP Technical Publication No. 3.
1Berger, A.J. 1972. Hawaiian Birdlife. Honolulu: The University Press of Hawaii.
2Grant, G.S., J. Warham, T.N. Pettit, and G.C. Whittow. 1983. Reproductive behavior and vocalizations of the Bonin Petrel (Pterodroma hypoleuca). Wilson Bulletin 95(4):522–539.
3Harrison, C.S. 1990. Seabirds of Hawaii: Natural History and Conservation. Ithaca, NY: Cornell University Press.
4Niethammer, K.R., J.I. Megyesi, and D. Hu. 1992. Incubation periods for 12 seabird species at French Frigate Shoals, Hawaii. Colonial Waterbirds 15(1):124–127.

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