SHIPBOARD SURVEYS OF MARINE BIRDS 



described by Heinemann (1981). Always check the range- 

 finder during the cruise with objects whose distances can 

 be verified by radar or other means (e.g., other ships or 

 buoys). See Siniff et al. (1970) for another useful type 

 of range-finder. 



On small ships and where the horizon is not visible, 

 a good technique is to trail a cylindrical buoy or other 

 marker behind the ship so that it is 300 m behind the 

 observer. Use floating line that will not stretch too much 

 and has several hundred pounds breaking strength. Ship 

 followers may congregate around this buoy enabling the 

 observer to keep track of them as well as judge the size 

 of birds at a known distance. If the ship's speed is known, 

 estimates of distance can be checked by timing how long 

 it takes to approach a floating object. When the ship is 

 approaching floating objects such as logs, buoys, trash, 

 or even birds, observers should estimate when the ship 

 is an arbitrary distance (e.g., 300 m) and time how long 

 it takes the ship to reach the object. By matching the 

 resulting figures with those in Table 1, observers can 

 check their estimation of distances. Be aware that cur- 

 rents affect the estimate depending on the relative direc- 

 tions of the ship and current. 



Duration of Observations and 

 Length of Transects 



The duration of observations not only affects the amount 

 of area surveyed, but several other important variables, 

 especially frequency of occurrence. Short transects cover 

 small areas, but provide a large sample size. Long tran- 

 sects are less likely than short transects to miss uncom- 

 mon species, thus they reduce the sometimes severe 

 problem of accumulating many transects with no birds; 

 many transects without sightings compound the difficulty 

 of analyzing the data. Short transects allow observers to 

 count bird numbers in rapidly varying habitats and have 

 the advantage of being easier to fit into a tight schedule 

 or into small bays and fjords, while long transects have 

 the advantage of requiring less paper work per set of 

 observations not an inconsiderable problem. In the past, 

 we have used both 10- and 15-min transects. We now use 

 only 10-min transects. Remember that the greater the 

 variability within or between data sets, the more difficult 

 the data are to analyze and compare. 



Counting Birds 



Detecting and identifying birds at sea is a skill that 

 has to be developed. Do not depend on your naked eyes 

 to spot birds. Make frequent sweeps of the entire count 

 area with your binoculars. Scanning forward to the end 



Table 1. Number of seconds* required for a ship to 

 cover specific distances at selected speeds. 



of the transect increases the chance to detect birds that 

 may leave the area or dive before the ship reaches them. 

 For birds on the water, be sure to count them as far in 

 front of the ship as possible, since they may dive or 

 move out of the transect zone as the ship approaches. Keep 

 time in mind however; as the transect end approaches, 

 the forward scanning distance becomes progressively 

 shorter. Look over the same area more than once. Many 

 alcids remain under water for a long time and may not 

 be seen on the first, or even second, scan. Some birds 

 may be located and identified by sound. In Alaskan 

 waters, the most easily heard and recognized call is the 

 contact note used by marbled murrelets (Brachyramphus 

 marmoratus). 



The objectives of the study will dictate whether em- 

 phasis will be placed on counting individuals or identify- 

 ing species. In general, it is more important to detect birds 

 and accurately enumerate them than it is to identify them. 

 For example, it is more important to count all murres 

 (Uria spp.) than to spend excessive amounts of time try- 



