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BIRD SURVEY TECHNIQUES

BIRD SURVEY TECHNIQUES

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BIRD SURVEY TECHNIQUES

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  1. BIRD SURVEY TECHNIQUES Based on the manual prepared by Salim Javed & Rahul Kaul Bombay Natural History Society

  2. WWhy Count Birds? • Fundamental questions • Elemental arithmetic tendency to count • Necessary to devise a strategy and new plans • Doing something in a systematic manner • Interesting and necessary to know more about birds

  3. WWhere to count? • Any area – garden, orchard, park, forest, wetlands, grassland, desert • Unstudied area • Important staging area • Threatened area • Sanctuary or a national park • Research site(s)

  4. WWhen to count birds? • Breeding season • Winter counts • Seasonality and timing of count is very important • During migration

  5. How to plan a survey •  Permission from forest department/ relevant authority •  Make local contacts •  Logistics i.e. places of stay, routes etc •  Necessary funds •  Area maps: Toposheets, vegetation maps, aerial photos •  Literature (checklist of birds and plants, reports, research • papers, working plan) •  Data sheets, pen, field note book, pad •  Equipment: Binocular, camera, compass, altimeter, GPS •  Fieldguides, reference books and papers

  6. Which site(s) to select We have to ask the following questions: What is the purpose of census?  IBA or EBA  Sanctuary or National Park Size: logistics, time frame, budget and the size of the team

  7. Strategies A. Non-sampling strategy  Total count in an area e.g. Siberian cranes in Keoladeo  Nest count e.g. Greater Adjutant stork colony  Territory mapping e.g. Bengal florican display grounds

  8. Sampling strategy • Counting a small representative population and • then extrapolating about the total population • e.g. random, stratified or systematic random

  9. Important points to remember -  Do not unnecessary collect large data  Maximize your efforts  Determine sample size  Collect right type of data

  10. To determine effective sampling efforts, first answer - Two major questions 1. How many samples to take? 2. What should be the plot size so that most species are covered ? To answer these questions, we need to plot Species Discovery Curve. Species Discovery Curve is plotting of number of species detected or discovered per unit of sampling efforts (length of transect, time spent walking a transect or standing on a point).

  11. Species discovery curve showing a cumulative total of species seen in riparian habitat in Dudwa National Park, India over a 30 day period

  12. What is distance sampling? Distance sampling involves collection of data where distances of objects are estimated or measured. e.g. Line transects Point Counts Cue counts (calls, territory)

  13. WWhat is Line Transect ? Line transect is based on the theory of walking along a predetermined route at a regular interval to record the Birds on or near the line.

  14. Methodology or Study Design • Site Selection •  Random or systematic •  Stratified : covering different habitats within the study area •  Stratified random: randomly choosing areas in different habitats

  15. B. Where can one monitor Line Transects?  Best in open, flat habitat  Also conducted in hilly areas  Homogeneous habitat preferred C. Where to place Line Transects  accessibility and terrain  straight line, not zig-zag  avoid along roads, streams or contour of hills  well spaced out (minimum 200 m apart)  random, stratified or linear (hilly terrain)

  16. D. Permanent or Temporary transect If permanent -  mark with stones or colour posts (trees)  divide the transects in to 40-50 m segments E. What should be Transect Length? It varies according to species, habitat and aim of study single species study  community study  rare or common species diversity of habitat How to determine transect length?  preliminary checklist  few test runs  species area curve

  17. What is Species Area Curve ? Species area curve is drawn by plotting the sighting frequency of birds with increasing transect length. After a point, species discovery curve tends to stabilise, which means that with subsequent increase in the line of the transect there is little or no corresponding increase in the new species being added. The point at which curve flattens out (asymptote) can then be considered as adequate for sampling birds.

  18. 200 300 400 500 600 700 • Transect Length in meters 35 S P E C I E S 5 Species area curve for obtaining the length of the transect

  19. E. What should be the speed of travel?  walk in standard pace (about 8-10 m/minute)  time duration should not vary more than 10% among transects F. What time of the day?  preferably morning  15-25 minutes after sunrise  continue for 2-3 hours G. In which weather condition? sunny weather  avoid raining or windy days  keep tract of weather condition of study area

  20. H. How often (periodicity) ?  weekly or fortnightly or monthly (intensive study)  seasonal (long term study, 5-10 years)  once or twice a year (very long term study, 20-25 years or more) I. How many replicates ? Minimum two replicates of each transects  Minimum of 6 monitoring in each season J. Open width or fixed width ? Open width: All birds are noted irrespective of their sighting distance  Fixed width or Belt transect: Birds seen up to a certain distance (width on either side of transect length) are only noted

  21. Biases in census counts Observer bias  Effect of habitat  Bird behaviour  Weather How to do analyses of the collected data? A. Simple method :n D= ----------------- 2L x Y n= total number of individuals; L=length of the transect; Y= mean perpendicular distance B. Computer programmes: 1. TRANSECTS-II 2. DISTANCE

  22. How to determine the width distance? It depends upon the birds being censused and type of habitat. Data collection What to record ?  number of individuals of a species  perpendicular distance  sighting angle and sighting distance  sex (male, female if possible)  age (adult, juvenile)  activity (singing, foraging, flying, etc)  substratum (ground, bush, tree etc) If the bird is not seen but heard, records its call and try to judge the distance.

  23. 15 I ND I V I DUAL S 2 Perpendicular Distance Frequency histogram of perpendicular distances (number of individual detected decrease with increasing distance from the line)

  24. Question: What is perpendicular distance? Answer: Perpendicular distance is the distance of the bird from the transect line. Should we record the exact distance? Recording exact distance is difficult (e.g. 11 m, 16 m) Therefore, record in group intervals (0-5m, 5-10m, 10-15m).

  25. PD= Perpendicular Distance SD= Sighting Distance O= Observer L= Transect Line = Object  PDSD L  Recording of perpendicular distances and sighting angles in line transect sampling

  26. The Fourier series (FS) estimator used in the analysis is the expansion of probability density function (pdf), f (x). Fourier series estimator is a robust non-parametric procedure in which the difference in detectability between different habitats is taken care of by pooling robustness of FS estimator and its estimation efficiency. n F (0) D = --‑‑‑‑‑‑‑------ 2L n = Total number of bird groups seen; L = Length of the transect F (0) = Probability density function

  27. N= No of objects L= Length of transect Y= Mean perpendicular Distances 10, 12, 15, 5, 10, 25 N = 6 L = 500 Y = 12.8 D = n / 2LY = 6 / 2 x 500 x 12.8 = (6 / 12800) x 10000 = 4. 6 birds / ha A simple way of calculating density from ungrouped perpendicular distances

  28. Advantages of Line Transect ·More economical  Greater species turnover ·Larger area is covered in relatively shorter time Applicable throughout the year  Permanent transects can be monitored for a longer period of time  Can be used in most of the habitat types (except wetlands) With little care can also be used for hilly terrain Disadvantages of Line Transect ·Distances are not correctly measured ·Movement of observer may disturb the birds ·Chances of missing skulking or shy birds are great

  29. Assumptions of Line Transect  No bird is missed  Transect is a straight line  Every detection is independent  Points/objects are fixed at initial sightings and they do not move before being detected

  30. Precautions to be taken:  Try to keep line as straight as possible  Make special effort to find those birds that are close to the transect  Distances should be measured correctly  Transect should be long enough to allow detection of at least 40 individuals  Transect should be representative of a habitat  Observer must be interested, competent and trained

  31. Point Count Method Point Counts can be imagined as transects of zero length conducted at zero speed. Types of Point Count: 1. Plot Counts (fixed radii for all species) 2. Point Counts with variable radii, by species 3. Point Counts with unlimited radii (Total Counts)

  32. What are the assumptions?  birds do not approach the observer or flee.  all the birds are detected at the point of the observer.  birds do not move much during the count period  birds behave independently of one another.  distance estimates are accurate  birds are fully and correctly identified.

  33. Advantages of Point Counts  less time consuming  duration can be controlled  total attention to detect birds  small homogenous habitats can also be studied Disadvantages of Point Counts generating bird list is slower  many species are missed  area sampled in one unit is small

  34. How to select points for counting ? •  Points to be counted are to be laid out systematically or • selected randomly in the study area. •  Points should ideally be 200 meters apart to avoid double • counting. •  In a small area, lesser points should be monitored to • avoid duplication •  In small patches of habitat, inclusion of points near the • edges should be done with caution depending on the • objectives of the study.

  35. What should be the Count duration?  It can vary from 2-20 minutes Record only these birds seen during Count duration. Do not include for analysis those birds seen while walking between two points. How far Point counts should be done ? Not very far (> 200 m)  Not very close (<20 m)  Ideally 50 to 100 m apart

  36. At what time it should be done ? 15-20 minutes after sunrise  Evening counts can be done How to record distance ?  Record bird’s distance from the observer (yourself) Record distance in categories (0-25m, 25-50m and >50m)

  37. Data recording • 1. Number of individuals of each species detected within a 20-25 m radius surrounding the observer. The radius will vary depending upon the habitat type. • 2. Number of individuals of each species detected beyond the 25m radius but still within the same habitat. • 3. All individuals detected while the observer walked between count points are recorded but the data are not used in the analysis. Species recorded during this period will contribute to the completeness of species list for the site. • 4. Birds that originally were detected outside 20-25m radius boundary but later move within 25m of the observer are recorded as occurring within the fixed radius circle. This facilitates comparison among vegetatively different habitats. Objective is to count each individual bird once and only once.

  38. Analysis • density, species diversity, richness and species composition • can be calculated •  enter large data in EXCEL and LOTUS •  sample data matrix can be generated using SPECDIVRS.BAS. •  follow the instructions given in statistical books and/or • take help of a good bio-statistician

  39. POINT COUNT • Date Locality Altitude Habitat Observer Salim • Lat Long Slope Weather Sheet # • Time Start Time End Visibility Aspect • Sr. No. Bird Species Time No. Sex Age Distance Height Activity Plant spp. Hgt. Remarks • Blue Whistling Thrush 0710 2 - - 10 m 0 m Foraging - - • 2. Minivet 0810 4 - -- 5 m 1 m Foraging - - • 3. • 4. Example of a data sheet for point count used in Ranikhet, Kumaon Himalayas

  40. Comparison of transect and point count census methods ____________________________________________________________________________________________________ S. No. Items Transects Point Counts Duration ____________________________ Short Long ____________________________________________________________________________________________________ 1. Saturation of observer with cues from bird Little Some Much 2. Birds moving into and out of the range Few Some Many 3. Speed of generating species list Fast Medium Slow 4. Birds missed by flushing No Yes Yes 5. Skulking birds missed Yes No No 6. Total count/unit line Same Same Same 7. Attention divided Yes No No 8. Area sampled in one unit Large Small Small 9. Bias Small Small Small 10. Precision High High High ____________________________________________________________________________________________________ Desirable method= Small bias and high precision

  41. Species Richness Methods Species richness methods are simple methods of counting or generating species list and then making useful interpretation from them. Depending upon the area, type of survey, whether single species or multi-species, a species richness method can be conducted. Types of species richness methods 1. Encounter Rates 2. McKinnon’s Species Richness Method 3. Timed Species Count 4. Mist netting

  42. 1. Encounter Rates  species seen per unit efforts (time, distance etc)  useful for single species or multiple-species surveys  data gives only relative abundance not density It gives number of birds/unit area or number of birds/unit time that can be compared with other habitats/areas/seasons.

  43. Data sheet for collecting encounter rate data DATA SHEET __________________________________________________________________________________ Date Locality Habitat Time Start Time End Weather Visibility Aspect Slope Altitude Coordinates Observer SJ Transect/Trail Length Transect # Sheet #   __________________________________________________________________________________ Bird Species Time Flock Size Habitat Sex Age Activity    __________________________________________________________________________________ Roseringed Parakeet 0645 2 MF M A Perching Redvented Bulbul 0650 1 MF - SA Feeding Green Bee- eater 0700 4 MF - A Perching Data Sheet

  44. A common method of presenting encounter rate data ________________________________________________________________________________________________________________________________ Sites No. of birds No. of hours Birds/hour Transect Length Birds/km ________________________________________________________________________________________ Site 1 2 5 2/5 3km 2/3=0.6/km Site 2 3 2 3/2 2km 3/2=1.25/km Site 3 5 3 5/3 2km 5/2 = 2.5/km ________________________________________________________________________________________

  45. How to present multi-species survey data?  Calculate encounter rate of each species  Enter data in EXCEL or LOTUS  Present data in descending order or classification-wise  Categories the encounter rate (very common 20-25 sightings; common 15-20 sightings; etc)

  46. Encounter rates from a multi-species survey from a standard one hour walk at each site ________________________________________________________________________________________________________________________________ Species Site 1 Abundance Site2 Abundance ______________________________________________________________________________ Rose-ringed Parakeet 5 5/hr 2 2/hr Ring Dove 2 2/hr 1 1/hr Green Bee-eater 0 0/hr 2 0/hr Emerald Dove 4 4/hr 1 4/hr Red breasted Flycatcher 1 1/hr 0 0/hr _____________________________________________________________________________________________________________________ Common: 5-10; Very Common: 10-25; Uncommon: 1-5

  47. Advantage of Encounter rate data quick and easy method, especially in hilly terrain  easy calculation  data comparable across sites/seasons/habitats  diversity and richness can be calculated

  48. 2. McKinnon's Species Richness Method  developed by McKinnon & Philip (1993) in Indonesia.  quick and easy to know richness  useful for rapid surveys in difficult habitats  useful for multi-site surveys

  49. What is the methodology? walk in an area till a given number of species are recorded  the number of species could be 10, 15, 20, 25 or 30  but it should be constant for all the sites  once a given number of species(e.g. 20) have been seen, go to another area and record the same number of species (i.e. 20).  prepare 10 to 15 such lists from different parts of the study area  common species will get recorded in several lists.  in species rich areas, listing will be very fast  note starting and ending times, habitat condition, weather etc.

  50. Analysis By plotting the cumulative total of species detected against the number of lists, species discovery curves can be produced.  This species discovery curve for each site is a measure of species diversity and can be plotted to compare several sites  If additionally numbers of individuals are also recorded these values can be used to compare species diversity based on discovery curve but also indices of richness and diversity.  Number of time a species reappears in subsequent lists can be converted into frequency of occurrence, which gives some idea about relative abundance of that species when compared with other species.  An index of relative abundance can also be generated by dividing the number of lists a species appears in by the total number of lists. An index between 0-1 is produced for each species.