Student: Lily LiewSEE-U 2001, Biosphere 2

Professor James Danoff-Burg

Professor Tim Kittel

T.A. Erika Geiger

Impact of Human Activity on Birds Observed at Two Arroyos

INTRODUCTION

PRIMARY QUESTIONS

•Does human activity impact the abundance and richness of animal species? •If so, how does it affect the abundance and richness?•If not, what factors other than human activity could impact the abundance and richness of animal species?

Above: Site One, High Disturbance Arroyo

HYPOTHESIS•As human activity increases, animal species abundance and richness decrease.

CONTEXT OF STUDY

•Become better informed how lessen adverse impact of humans

•Apply knowledge to responsible land use planning and minimize loss of animal species

•Two arroyos selected on campus.

•Arroyos are riparian communities with high biodiversity; ideal to contrast high impact vs. low impact human activity

• 2 Arroyos located elevation of 1150 meters, 32.6°N latitude, 110.9°W longitude

•High impact arroyo•Distance to road 19 m to 76 m•Near housing and insectory; ornamental vegetation; less dense growth

•Low impact arroyo•Distance to road 425 m to 535 m•Denser vegetation, less open space

•Data collected over 8 mornings (2 dropped b/c monsoon), bet. 04:45-06:45 hours •Summarized on Excel•Analyzed on non-parametric tests (Mann-Whitney Test and Kruskal-Wallis Test)

METHODS

METHODS (CONT’D)

Summary

1)   3 sites selected at each arroyo, total of 6 sites:

– high impact arroyo--site 1 behind student houses (Arroyos #14 and #15); site 2 opposite student union building; site 3 next to the insectory.

– low impact arroyo—all 3 sites parallel to the barb wire fencing

2)   Measured 24 meter by 15 meter area for each site

3)    Binoculars and bird guidebook used to observe birds for 1.5 hours between 04:45 to 06:45 hours

4)    Trees counted within the 24 meter by 15 meter area of each site

Map of Sites

Topographical map of six sites along both arroyos (A=high impact; B=low impact)

RESULTS

High Impact Arroyo• More species and individuals observed at high impact arroyo (see Fig. 1)•At each site, average of 9.7 bird species and 21.3 individual birds were observed (see Fig. 2). •As distance from human activity increased, number of individual birds and species richness decreased (see Fig. 3).

Low Impact Arroyo•Fewer species and individuals observed at low impact arroyo (see Fig. 1)•At each site, average of 6 bird species and 9.7 indivudals were observed (see Fig. 2)•As distance from human activity increased, number of individual birds and species richness decreased (see Fig. 3).

•Species abundance was not significantly different between the two arroyos (Mann-Whitney Test, Z

1,4= -1.528, P=0.127). •Low disturbance arroyo had a significantly lower species richness than the high disturbance arroyo (Mann-Whitney Test, Z 1,4= -2.087, P=0.037). •Site three from the high impact arroyo did not differ significantly from three sites at the low impact arroyo (Kruskal-Wallis Test, Chi-Square 1,3=0.392 number species of birds; Chi-square 1,3=0.392 number individual birds). These four sites similar in vegetation and tree density; fewer species and individuals than first two sites at high impact arroyo

( Site 3, High impact arroyo)

Total Number of Species and Number of Individuals

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Figure 1: Sites 1 to 3 are high impact sites and sites 4 to 6 are low impact sites. Sites 1 and 2 had a significantly higher number of bird species than sites 3 to 6.

Figure 2: High Impact sites had higher average number of species and abundance than low impact sites;there was greater variation from the average value for individual birds than for individual species for both low

impact and high impact sites. Error bars indicate standard average (standard deviation/square root of n samples)

Average Number Species of Birds and Average Number of Individual Birds

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Number of Species and Number of individuals vs. Distance to Road

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Linear (# Species ofbirds)Linear (# of individualbirds)

Figure 3: As distance from road increases, number of species and number of individuals decreases

DISCUSSION

Site One, Low Disturbance Arroyo

• Unexpected results: fewer birds seen at the low disturbance arroyo than at the high disturbance arroyo.

•Human activity can increase rather than decrease bird species richness and abundance, eg. in suburban areas (Blair, 1996)

•Certain levels of disturbance can be optimal for species diversity (Jullien et al., 1996).

•This study did not consider the level of human impact at each arroyo.

•Other factors that could influence results:

•Construction noise at low impact arroyo could affect number of birds observed

•More mesquite trees at low impact arroyo=more camouflage; harder to see birds

•Birds at low impact arroyo may be more wary

DISCUSSION (Cont’d)

•“Urban exploiters” and “suburban adaptables” adapt well to urbanization, unlike “urban avoiders; birds at high impact arroyo could be “suburban adaptables”

•Moderate development leads to an increase in ornamental vegetation, water sources, primary productivity and amount of edge between habitats; benefit species adaptable to human activity.

•Species richness optimal at intermediate levels of disturbance; beyond levels, species richness starts declining as forest fragmentation increases, and forest patches become smaller and more isolated (Jullien and Thiollay 1996). More cleared ground at high impact arroyo: more space for flight; also food left out by humans

•Third site at high disturbance arroyo similar to three sites in the low disturbance arroyo; all four sites have denser growth, less space for the birds to fly around in, not easily seen

• Species abundance not statistically significant. Need additional sites each arroyo.

•Possible errors include not enough sampling points, misidentification of species. More data would have to be collected, more sites should be added to each arroyo, and more observations

CONCLUSION•Human impact can result in significantly higher species richness than low impact.

•Human impact can increase species richness and abundance to an optimal level beyond which it starts to decline (Jullien et al, 1996); intermediate impact level appears optimal

•Increase in species richness has been linked to moderate development which leaves sufficient patches of native land and vegetation for animal species to use, and yet provides improved resources

•High impact arroyo in this study could be classified as a moderate impact

•Species richness could be influenced not only by human factors, but also by native vegetation growth and size of native land patches

• Low impact arroyo in this study had more dense vegetation not favoured by some birds

•Land use planning could examine what types of animal species would be most affected by human activity, and plan accordingly to minimize the negative impact of human activity and preserve native habitats required by certain animal species (Blair, 1996; Recher and Serventy, 1991).

Blair, Robert B. 1996. Land use and avian species diversity along an urban gradient. Ecological Applications 6(2):506-519. 

Gill, Jennifer A., W. J. Sutherland, A. R. Watkinson. 1996. A method to quantify the effects of human disturbance on animal populations. Journal of Applied Ecology 33(4):786-792. 

Jullien, Mathilde and Jean-Marc Thiollay. 1996. Effects of rain forest disturbance and fragmentation: comparative changes of the raptor community along natural and human-made gradients in French Guiana.” Journal of Biogeography 23(1):7-2 .

Peterson, Roger Tory. 1961. A field guide to Western birds. 2nd Edition. Houghton Mifflin Company, Boston.

Phillips, Steven J. and P. W. Comus, eds. 2000. A Natural History of the Sonoran Desert. Arizona-Sonora Desert Museum Press, Tucson. p.8.

Recher, H.F. and D.L. Serventy. 1991. “Long term changes in the relative abundance of birds in Kings Park, Perth, Western Australia.” Conservation Biology 5(1):90-102.

Warkentin, Ian G., R. Greenberg, and J.S. Ortiz. 1995. “Songbird use of gallery woodlands in recently cleared and older settled landscapes of the Selva Lacandora, Chiapas, Mexico.” Conservation Biology 9(5):1095-1106.

REFERENCES

Many thanks to all the instructors for their assistance!

Acknowledgements