what is lacking in the known art is a method and apparatus to filter the water supply in a birdbath in a manner that is both convenient and sanitizes the water supply to prevent either stagnation or other forms of biological infestation . the present invention responds to these objectives . generally , the present invention comprises a method for filtering water used in a birdbath by passing the water through a filter disposed above a reservoir of water . once the water is filtered , it is returned to the reservoir . the act of filtering the water may comprise either removal of particulate matter from the water , sanitization of the water , or both . the present invention comprises a method for receiving water from the reservoir , pressurizing the water and delivering the water to a bathing bowl . this step of delivering the water to bathing bowl may further comprises creating a cascading shower that helps to aerate the water supply . the present invention may further comprise steps for agitating the water present in the bowl in order to cause particulate matter that may have accumulated at the base of the bowl to float to the surface level of the water present therein . this step helps particulate matter suspended in the water or accumulated in the base of the bowl to migrate toward filters disposed above the water reservoir . fig1 is a cross - section of one illustrative embodiment of a birdbath according to the present invention . in this illustrative embodiment , a birdbath comprises a pedestal 10 that is used to support a bowl 15 . the pedestal 10 comprises the main reservoir 20 that is used to contain a volume of water . in this illustrative example , the main reservoir 20 is sized to accommodate five gallons of water . it should be noted , though , that the overall size of the birdbath can be varied according to specific architectural requirements or to accommodate specific application needs . also , the bowl 15 and the pedestal 10 may be manufactured as one integral unit wherein alternative means for conveniently changing a filter can be provided . this type of alternative embodiment is described infra . the cross - section of this illustrative embodiment depicts that a pump 25 is disposed in the volume of water contained in the reservoir 20 . in some embodiments , the pump 25 is supported away from the bottom of the pedestal by a pump support grate 30 . it should be noted that supporting the pump 25 away from the bottom of the pedestal 10 is entirely optional . the purpose of supporting the pump 25 away from the bottom of the pedestal 10 is to help preclude entry into the pump 25 of large particulate matter that may accumulate in the sump volume 22 of the pedestal 10 . many embodiments of a birdbath according to the present invention actually dispose the pump 25 at the bottom of the pedestal 10 directly in the sump volume 22 . one such alternative example is described infra . the pump 25 comprises a water intake 35 . in operation , water from the main reservoir 20 enters the pump 25 through the water intake 35 . the pump 25 imparts pressure onto the water and discharges the water through a pressure hose 40 . the pressure hose 40 delivers pressurized water from the pump 25 to a sprinkler assembly 45 . the pressurized water is discharged from the sprinkler assembly 45 to create a cascading shower of water . it should be noted that the sprinkler assembly 45 is purely optional and that any means to direct the pressurized water into the bowl 15 is an acceptable alternative embodiment of the present invention . as water begins to fill the bowl 15 , the level of the water in the bowl ( depicted as the bowl - water - level 50 ) will rise to a height established by a return riser 55 . the return riser 55 comprises a section of tubing that establishes a return - path 56 for water from the bowl 15 to return back into the pedestal 10 . the return riser 55 continues downward through the base of the bowl 15 and allows water to fall back into the pedestal 10 . as water falls back into the pedestal 10 , it encounters a particulate filter 60 . the purpose of the particulate filter 60 is to remove contaminants from the water returning into the pedestal 10 . water passing through the particulate filter 60 encounters a sanitizing filter 65 . the purpose of the sanitizing filter 65 is to neutralize biologically active matter suspended in the returning water . it should be noted that the illustrative embodiment described here comprises both the particulate filter 60 and the sanitizing filter 65 . however , in other embodiments , the particulate filter 60 may not be provided and only the sanitizing filter 65 comprises the invention . in yet other embodiments , the sanitizing filter 65 may be omitted and the invention comprises only the particulate filter 60 . in this example embodiment of the present invention , the particulate filter 60 comprises a polyester filter akin to those commonly used in an air conditioning return path . it should be noted that any suitable material may be used to impeded the passage of particulate matter suspended in the returning water . also in this example of embodiment , the sanitizing filter 65 comprises an activated - carbon filter commonly used to filter drinking water . again , and in the true spirit of the present invention , any suitable sanitizing filter can be used to cleanse the water returning from the bowl 15 . once the water passes the particulate filter 60 , if such a particulate filter is provided for in a particular embodiment of the present invention , and once the water is sanitized by a sanitizing filter 65 in those embodiments of the present invention that comprise the sanitizing filter , the water is discharged back into the main reservoir 20 comprising the pedestal 10 of this example embodiment . in this example embodiment , either the particulate filter 60 and / or the sanitizing filter 65 are supported by a filter grate 70 . the filter grate 70 is disposed slightly above the water level found in the main reservoir 20 . the water level in the main reservoir 20 is referred to as the reservoir - water - level 75 . as already discussed , support grates are used to hold the pump 25 away from the sump volume 22 found in the lowest portion of the pedestal 10 and to fix either the particulate filter 60 and / or the sanitizing filter 65 above the reservoir - water - level 75 . the pump support grate 30 is supported vertically around its perimeter by a first contoured ledge 80 . the second contoured ledge 85 supports either filter above the reservoir - water - level 75 . in this example embodiment , the pedestal 10 comprises contoured ledges because the contoured ledges result in an aesthetically pleasing contoured profile at the pedestal &# 39 ; s 10 external surface . it should be noted that any means to support either the pump support grate 30 or the filter support grate 70 can be used in alternative embodiments of the present invention . it should also be noted that any supporting means used to support the pump support grate 30 or the filter support grate 70 need not necessarily support these grates around their entire perimeter . as an additional note , the example embodiment described here suggests that a pedestal and shallow bowl 15 is circular . the present invention should not be limited in scope to any particular geometric shapes that may comprise a birdbath according to the present invention . again referring to fig1 birds 100 visiting the birdbath may bathe in the water or they may drink water found in the bowl 15 . as birds made do , biological wastes may be deposited in the water found in the bowl 15 . particulate matter , i . e . excrement , will inevitably be deposited in the bowl 15 . some particulate matter may float to the surface of the water found in the bowl 15 and other particulate matter may collect at the bottom of the bowl 15 . to prevent the collection of particulate matter at the bottom of the bowl 15 , the invention may further comprise an agitating jet 105 that emit a strong stream of water 110 toward the bottom of the bowl 15 . this strong stream of water 110 agitates the particulate matter collecting at the bottom of the bowl 15 forcing it to the water &# 39 ; s surface . it should be noted that the present invention may comprise one or more agitating jets 105 . one disadvantage exhibited by the invention in a configuration comprising an agitating jet 105 is siphon - drainage of the bowl 15 when the pump 25 is turned off . in the absence of the agitating jet 105 , the water level and the bowl will be maintained at the height of the return riser 55 when the pump 25 is turned off . in most example embodiments that comprise an agitating jet 105 , the agitating jet will be disposed below the height of the return riser 55 . when the pump 25 is turned off , the water level in the bowl 15 will recede to the level of the agitating jet 105 because of back - flow . to preclude this effect , the invention may further comprises a back - flow preventer 42 disposed in the line with the pressure hose 40 . the back - flow preventer 42 prevents siphoning of water present in the bowl 15 so that the water level can be maintained at the height of the return riser 55 when the pump 25 is turned off . fig1 a is a pictorial depiction of the capillary action found at the entry of a return riser comprising one example embodiment of the present invention . once particulate matter is either floating on the surface or has been forced to the surface by an agitating stream of water 110 , it passes into the water return path 56 formed by the return riser 55 . the return riser 55 exhibits a capillary effect with respect to water flowing from the bowl 15 into the return path 56 . this capillary effect allows particulate matter to flow freely over the perimeter of the return riser 55 . the agitating stream of water 110 promotes the passage of particular matter into the return path 56 because agitation of water in the bowl 15 causes irregularities in the surface tension of the water present in the bowl 15 . this , of course , causes variations in the level of capillary action . fig2 is a pictorial view depicting the structure of a split support grate used in one example embodiment of the present invention . in the example embodiment of a pedestal as described here , the circular geometry of the pedestal and the use of contoured ledges to support the grates used to support the filters and pump precludes the use of one - piece support grates . accordingly , each support grate is split into two semi circles 130 . each semi circles is physically small enough to pass through the opening of the pedestal 10 and can then be positioned onto either the first or second contoured ledges ( 80 and 85 respectively ). the support grates used in this example embodiment of the present invention are fabricated from a polystyrene plastic and comprise a mesh of approximately one - half of an inch . again , the actual structure of the support grates is not pertinent to the utility of the invention as specified herein . any suitable support mechanism may be applied . fig3 is a pictorial representation of the top view of a shallow bowl according to one example embodiment of the present intention . according to this example embodiment , the sprinkler assembly 45 is disposed approximately in the center of the shallow bowl 15 . again , the actual location of the sprinkler assembly 45 can be varied . in this illustrative embodiment , the return riser 55 is offset from the center of the bowl 15 . again , the actual placement of the return riser 55 can be varied . for the sake of manufacturing convenience , an agitating jet 105 is made as an appendage to the sprinkler assembly 45 . the actual placement of any agitating jet 105 can be varied in order to maximize the effectiveness of a water stream 110 emanating from the jet . hence , agitating jets 105 may be placed anywhere in the bowl 15 either proximate to the center of the bowl or around its periphery or anywhere where the efficacy of water agitation can be maximized . fig4 is a cross - section of a simplified pedestal according to another example embodiment of the present invention . in this simplified version of the present invention , the pedestal 10 comprises a linear profile and further comprises a single support ledge 130 . in this simplified embodiment , the pump 25 is disposed at the bottom of the main reservoir 20 . akin to the first illustrative embodiment described herein , the pump 25 receives water from the main reservoir 20 through an inlet 35 . the pump 25 discharges pressurized water through a pressure hose 40 that delivers the pressurized water to the shallow bowl 15 . in this illustrative embodiment , the pedestal 10 may further comprise a filter replacement slot 135 . the invention according to this illustrative embodiment further comprises a filter cartridge 140 that is disposed above the main reservoir 20 being supported by the single support ledge 130 . accordingly , the filter cartridge 140 may be inserted through the filter replacement slot 135 in order to facilitate replacement of the filter system . in this alternative example embodiment , the filter cartridge 140 may comprise a particulate filter and / or a sanitizing filter commensurate with the specification thus far provided . in this illustrative embodiment , replacement of the filter can be accomplished through the filter replacement slot 135 . in other embodiments that do not provide such a slot , the shallow bowl 15 must be removed to gain access to the filter disposed above the water reservoir . hence , the shallow bowl must be a separate assembly so that it can be removed from the pedestal . in those embodiments that comprise the filter replacement slot 135 , the shallow bowl may be made integral with the pedestal forming a single piece birdbath . various materials can be utilized in the construction of a birdbath according to the methods and apparatus described herein . in one example embodiment , the shallow bowl 15 and the pedestal 10 comprises a baked ceramic material . either the shallow bowl 15 or the pedestal 10 may be constructed of plastic , bakelite , metal , fiberglass or any other suitable structural material . while this invention has been described in terms of several preferred embodiments , it is contemplated that alternatives , modifications , permutations , and equivalents thereof will become apparent to those skilled in the art upon a reading of the specification and study of the drawings . it is therefore intended that the true spirit and scope of the present invention include all such alternatives , modifications , permutations , and equivalents . some , but by no means all of the possible alternatives are described herein .