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Movements and features of birds and fish
A bird’s wing is similar to a wing of an airplane.It has a thick, rounded edge that points forward and thins outt the back or end of the feathers. This helps the wind or air glide over the wing more easily. The pressure above the wing is reduced and the greater pressure from below lifts it up. This is
called lift and is the same kind of movement that lifts a bird’swings as they move through the air.Drag and gravity help slow the bird and pull it back to
the ground. Gravity is the force that pulls the bird’s body towards Earth.
Birds are the only animals with feathers.Feathers are light, yet strong and help keep birds warm on cold days and cool when it is hot. There are different types of
feathers for different jobs. Contour feathers give the bird’s body its shape, and help it to fly, steer, and swim. Down feathers lie close the bird’s body and keep it warm or cool. The brightly colored feathers, usually on male birds help to attractmates, while the dull colored feathers, usually on females helpto camouflage the bird when it is caring for young.
Movement is amongst the most important of animal behaviors, because it allows animals to respond to conditions within their environment to increase growth, survival and reproductive success (Kahler et al. 2001). The scale and pattern of fish movement varies widely among species. Some of the longest and most directed movements are completed by anadromous[1] salmonids in North America rivers or the piracema in South America as they migrate from headwater streams as young fish to the ocean and then migrate back to their natal streams as adults to spawn. Most species of stream fish do not migrate to the ocean, but instead appear to establish home ranges of various sizes and occupy those ranges for various amounts of time. Species such as smallmouth bass (Micropterus dolomieu) or green sunfish (Lepomis cyanellus) spend a majority of their time within a home pool, but do make trips to up and downstream areas.Streams are dynamic systems due to frequent disturbances such as floods or landslides, and fish habitat distribution within streams is inconsistent.Under such conditions, fish that can move between patches can recolonize disturbed areas, find new, higher quality, or less competitive habitats, or can more readily avoid predation. Fish movement can also support finding critical resources that change throughout the year and throughout the life cycle of fishes. Spawning, feeding and overwintering habitats are often located in different stream reaches. In addition, habitats that are suitable for fry are often not suitable for adults so fish must move as they mature. Fish movement also allows fish to avoid unsuitable or suboptimal conditions such as seasonally dewatered areas, high stream temperatures or stream flows, or elevated pollution levels.

The movement of fishes can be affected by both the physical conditions of the stream and the composition of the fish community. In a study on the movement of three cyprinids (Notropis boops, Campostoma anomalum and Cyprinella venusta) current velocity, riffle length and predation threat were found to alter movement rates. Decker and Erman (1992) found that there were interspecies differences in physical and biological characteristics that were associated with movement within the Saghen Creek, California fish assemblage.  Changes in abundance indicated movement into and out of the study reach. For example, temperature affected the abundance of Tahoe sucker, decreased stream discharge increased rainbow trout abundance; and breeding affected the abundance of Tahoe sucker, Lahotan redside, and possibly mountain whitefish. 


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